The modern practice of economic research relies heavily on mathematical models that make it possible to reveal hidden regularities in statistical data and make forecasts on their basis. Linear models based on vector autoregression (VAR) are the most common. However, the relationship between time series in the economy is often difficult to identify, so non-linear autoregressive (NAR) models show more reliable results. Artificial neural networks (ANNs) are usually used for implementation of these models, but ANNs do not provide the possibility of estimating the forecast in the form of mathematical expectation and a standard deviation. Therefore, the model proposed in the article combines two blocks: VAR and NAR. NAR is used to construct a prediction for a given number of points, and VAR for estimating the forecast in the form of a mathematical expectation and a standard deviation. The evaluation of the model was carried out on the daily data: exchange rate USD / RUB and “Brent” oil from 1.01.2016 to 1.03.2017. The average accuracy of forecasting the trend for the dollar was 54.9%, for the oil prices it was 54.0%. In this case, the relative error in predicting the dollar rate was from 1.09% (for the first point) to 2.01% (for the tenth point); the relative error in forecasting oil prices was from 1.28% (for the first point) to 4.58 % (for the tenth point). Thus, the model showed accurate results when predicting dynamic series and can be used to solve other forecasting problems. In particular, it is expedient to use the model as one of the factors when making investment decisions. In addition, the evaluation of forecasts is done on the basis of testing the NAR block of historical data and on the basis of VAR block forecast in the form of mathematical expectation and standard deviation.

The paper is devoted to a new randomization method that yields unbiased adjustments of p-values for linear regression models predictors by incorporating the number of potential explanatory variables, their variance-covariance matrix and its uncertainty, based on the number of observations. This adjustment helps to control type I errors in scientific studies, significantly decreasing the number of publications that report false relations to be authentic ones. Comparative analysis with such existing methods as Bonferroni correction and Shehata and White adjustments explicitly shows their imperfections, especially in case when the number of observations and the number of potential explanatory variables are approximately equal. Also during the comparative analysis it was shown that when the variance-covariance matrix of a set of potential predictors is diagonal, i.e. the data are independent, the proposed simple correction is the best and easiest way to implement the method to obtain unbiased corrections of traditional p-values. However, in the case of the presence of strongly correlated data, a simple correction overestimates the true pvalues, which can lead to type II errors. It was also found that the corrected p-values depend on the number of observations, the number of potential explanatory variables and the sample variance-covariance matrix. For example, if there are only two potential explanatory variables competing for one position in the regression model, then if they are weakly correlated, the corrected p-value will be lower than when the number of observations is smaller and vice versa; if the data are highly correlated, the case with a larger number of observations will show a lower corrected p-value. With increasing correlation, all corrections, regardless of the number of observations, tend to the original p-value. This phenomenon is easy to explain: as correlation coefficient tends to one, two variables almost linearly depend on each other, and in case if one of them is significant, the other will almost certainly show the same significance. On the other hand, if the sample variance-covariance matrix tends to be diagonal and the number of observations tends to infinity, the proposed numerical method will return corrections close to the simple correction. In the case when the number of observations is much greater than the number of potential predictors, then the Shehata and White corrections give approximately the same corrections with the proposed numerical method. However, in much more common cases, when the number of observations is comparable to the number of potential predictors, the existing methods demonstrate significant inaccuracies. When the number of potential predictors is greater than the available number of observations, it seems impossible to calculate the true p-values. Therefore, it is recommended not to consider such datasets when constructing regression models, since only the fulfillment of the above condition ensures calculation of unbiased p-value corrections. The proposed method is easy to program and can be integrated into any statistical software package.

The article is devoted to researching of the possibilities of applying multidimensional statistical analysis in the study of industrial production on the basis of comparing its growth rates and structure with other developed and developing countries of the world. The purpose of this article is to determine the optimal set of statistical methods and the results of their application to industrial production data, which would give the best access to the analysis of the result.
Data includes such indicators as output, output, gross value added, the number of employed and other indicators of the system of national accounts and operational business statistics. The objects of observation are the industry of the countrys of the Customs Union, the United States, Japan and Erope in 2005-2015. As the research tool used as the simplest methods of transformation, graphical and tabular visualization of data, and methods of statistical analysis. In particular, based on a specialized software package (SPSS), the main components method, discriminant analysis, hierarchical methods of cluster analysis, Ward’s method and k-means were applied.
The application of the method of principal components to the initial data makes it possible to substantially and effectively reduce the initial space of industrial production data. Thus, for example, in analyzing the structure of industrial production, the reduction was from fifteen industries to three basic, well-interpreted factors: the relatively extractive industries (with a low degree of processing), high-tech industries and consumer goods (medium-technology) sectors. At the same time, as a result of comparison of the results of application of cluster analysis to the initial data and data obtained on the basis of the principal components method, it was established that clustering industrial production data on the basis of new factors significantly improves the results of clustering.
As a result of analyzing the parameters of data partitioning into clusters using k-means and hierarchical methods using different distances, it was determined that the best result is obtained when using a combination of these methods, when in the first stage the number of clusters is determined by analyzing the visualization of hierarchical algorithms (dendrogram construction) , On the basis of which the division by the method of k-means is made. At the same time, a significant improvement in the quality of the partition is achieved by eliminating the emissions in the clustered data, and then including them in the analyzed set using discriminant analysis.
The application of this approach to the data of the structure of industrial production ensured good results. The resulting clusters are uniform in composition and meaningfully interpreted: the first cluster includes countries with low rates of output of the extractive industry relative to the cumulative output of the economy, with a sufficiently high value of this indicator in other sectors. In general, this group can be designated as a country with a developed industrial production of a high-tech type. The second group of countries with respect to other groups is characterized by a generally low share of industry in the economy, and in particular by lower rates of extractive industries. The third group of countries includes countries with a high resource base, which is characterized by a high share in the output of extractive industries.

The goal of the research is to prove repetitiveness of changes in the organization structure of commercial enterprises. With regard to the goals of the research, such scientifically well-known paired notions as vertical and horizontal; high and flat; mechanical and organic can be considered as two basic types of organizational structures. The authors’ hypothesis is that these two types of structures – consequent and parallel – replace each other dialectically, and change qualitatively in the process of enterprises growth, but, at the same time, they maintain their constitutive properties at each level of organizations development.
The retail sector was chosen as the object of analysis, since the generalized organizational structure in it is characterized by separate sales outlets, which makes it possible to conduct statistical processing of data. In this context, enterprises of similar size (in terms of number of employees and sales volume) and having similar (consequent or parallel) organizational structures can make groups that form the aggregate of commercial organizations. Cluster analysis is a generally accepted method of defining groups joining objects that are homogeneous with respect to certain criteria. Cluster analysis is the means of exploratory analysis, meant for natural clustering of the initial data set into groups. The IBM SPSS Statistics software was used for defining clusters.
The analysis was conducted according to the data of the Czech Republic retail enterprises. The economy of this Central-European country was chosen, because, on the one hand, it is a part of the common market of the United Europe, and, on the other hand, it preserves its national currency. The research data were obtained from the database of Albertina Gold Edition of Bisnode Česká republika, a.s., including enterprises of all the sectors. 1695 retail organizations of all sizes were chosen from the total trade organizations for the research.
As a result of the conducted analysis, six clusters were distinguished. When analyzing the average values of the variables in these clusters, they can be classified into four groups. The first group includes 1 105 small trade organizations with the fewest employees (in average, 5.4 people) and representing mainly retail traders or separate small shops. The second group (491 organizations) includes retail chains of small shops. The third group (70 organizations) includes quite large separate stores (supermarkets). In addition, the fourth group (29 organizations) includes large retail store chains (the average number of employees – more than 200, the average number of outlets – more than 23).
Overall, the results of the conducted cluster analysis prove the suggested hypothesis. But, of course, the given research should be considered only as the first step, and a more convincing confirmation of alternating consequent and parallel organizational structures requires a more detailed study, including the analysis of certain organizations’ structure. Nevertheless, the obtained results allow suggesting, that the common scheme of retail organizations evolution can be represented as a universal one, since the underlying approaches can be used taking into account the necessary peculiarities for retail organizations of any country with a market economy or a separate region.

The article justifies that in the conditions of stagnation in the Russian economy and the absence of prerequisites for its breakthrough development, it is necessary to seek new approaches in managing the development of economic systems.
The purpose of this article is to set the correct goal for the development of the domestic industry and to justify the mechanism for achieving it. A new approach is proposed in managing the strategic development of industrial enterprises, aimed at long-term growth of the quality of their technologies. It is proved that the implementation of such a strategy provides a benchmark for a quantitative indicator of the quality of human-machine systems – the economic level of their technology.
A number of methods for the strategic development of individual industrial enterprises and their systems based on economic and technological modeling of the development of industrial production are proposed. The tasks of managing the development of enterprises based on the criterion of maximizing their economic and technological quality and the need for state participation in the directed transformation of the country’s industrial complex are substantiated.
The need to ensure the linkage of strategies for the development of industrial enterprises with the strategy for the development of the economy as a whole is stressed.

The most part of stimulation methods in Russia are concentrated in legal documents of the regions of the Russian Federation. They directed on intensification of investment activity in regions. How similar are these investment stimulation conceptions? There is no mention in the literature of the methodical questions of quantitative analysis and inter-regional comparisons. In addition, there are no results of statistical research of inter-regional correlations of stimulation methods and analysis of dynamics of this process. There are no special measuring instruments. The presented work is aimed at completion of these blanks. The approach for the spatial correlation analysis of legislative norms is offered in research. Classification of investments’ stimulation methods is developed. The way of preparing and coding data for research is offered. The approach and system of coefficients for the analysis of inter-regional interrelations of legislative systems of investments’ stimulation is offered. A proximity coefficient of regional legislation, a factor of structure similarity and a dynamic coincidence index are proposed. The space-time base of investment stimulation methods on Russian Federation regions for 12 years is collected and statistically processed for research. There are only 758 documents. A source of texts is a site of the Ministry of Justice of the Russian Federation.
Research of documents has allowed revealing a number of laws in formation of regional investment stimulation systems. The regions that are the most similar in terms of structure of stimulation methods are identified. We have found the group of regions for which it is observed the increase in similarity of the legislation and the group with the reduction of similarity. Therefore, it is obvious that the general trend to reduction of similarity in the legislation takes place between Krasnoyarsk territory and the other regions of the Russian Federation. Calculations have revealed concurrence of dynamics to use some stimulation methods in Krasnoyarsk region and in the other regions of the Russian Federation for 2005 - 2016. Among them, there are some measures of subsidizing, concessionary terms of using the ground and granting of the ground areas, concession agreements on property and creation of industrial parks, state-private partnership and others. We have found the groups of regions in which there are the trends on harmonization or on a divergence to use the separate kinds of stimulation.
Thus, the offered approach and a set of measuring instruments enable to carry out the research of inter-regional similarity of legal documents. It allows receiving the answer to a question on a degree of similarity of systems of investment activity stimulation, accepted in regions; to estimate joint dynamics of stimulation systems’ changes; to define a degree of concurrence on separate measures of support; to analyze similarity of a current condition and processes on the change of the legislation. The approach permits to investigate directions of harmonization or a divergence of regional approaches to investment activity stimulation. The received results can form a base for the further economic-statistical and econometric researches of efficiency of methods for the investment activity stimulation. It will allow to structure objects of research, to allocate more homogeneous group of regions on stimulation methods. The proximity coefficient matrix will be especially useful in spatial econometric models. The offered approach and parameters can be applied to research the other positions of the regional legislation.

Research objective. Scientific research raises the problem of state support of peasant farms in Russia, consisting in disproportions in the structure of the budget subsidies of farmers, showing that a significant proportion of directions and types of budgetary allocations is provided by state support for lending to agricultural production.
On the one hand, this measure is directed to activization of agrarian policy on attraction of additional loan sources of financing. On the other hand, at insufficient interest of financial structures in agricultural industry, weak competitiveness of landowners with the banking sector, low availability of credit resources to the most part of producers, the specified support measures only promote growth of debt load of major agricultural firms and limit farmers in obtaining budgetary funds that does not increase their special legal status and the importance for agrarian economy, does not add social importance for rural territories, does not lead to increase in the general effectiveness in agricultural production and does not promote efficiency to use the means of support, and, therefore, demands formation basic other more effective approach to subsidizing of small farms in the village. Therefore, a research objective is justification and development of strategic models of structure optimization of the budgetary support of peasant farms, taking into account efficiency of measures, which relevance is confirmed by scientific research of the leading scientists in this subject area.
Materials and methods. The study used: data of state programs on agricultural industry during 2008-2012 and 2013–2020; analytical materials of national reports of their realization; statistical information resources of the Ministry of Agriculture of the Russian Federation; consolidated, individual financial and economic reports on agricultural producers of Penza region, which are processed by the methods of logical analytics, structural diagnostics, methodological synthesis of scientific research, the quantitative analysis and other economic-mathematical tools with the use of application programs of SPSS statistical package and mathematical Mathcad package.
Results. As part of the research econometric models of influence of the budget transfers on results of agrarian activity and development of peasant farms in terms of forms and types of the state subsidies, where functional dependences of revenues and profits from subsidies, allocated to support farmers are defined by 90% and 70% respectively, at the same time the budget transfers have the positive impact on the specified financial results. Based on the received coefficients of regression the model of structure optimization of the state support of farmers, which proceeds from maximizing a share of revenue from agricultural industry in a gross regional product, is constructed.
Conclusion. In the new look the structure of the state support of peasant farms will allow to increase greatly effect of use of budgetary funds, to increase efficiency of agricultural production, to increase the economic importance of country farms, to keep the social status of rural territories.

It is indicated that domestic economy is experiencing a shortage of investment.The acceleration of the processes of import substitution is one of the most important challenges facing the domestic economy at present.
Investments, especially capital investments and related investment relations constitute the basis for the development of the national economy and improving the efficiency of social production as a whole. A problem of formation of the amortization fundremains actual at the moment. In the modern scientific and educational literature amortization fund means the fund, including the use of funds to complete the restoration and repair of the fixed assets. This paper makesthe analysis of the situation in the area of investment in the fixed capital, which has developed in Russia for the past severalyears. The aim of this paper is to study the investment climate in the country based on the analysis of investments in the fixed capital by the sources of financing and types of the economic activity. The work is based on dynamic and structural analysis of analytical and statistical information on the processes occurring in this field.
As a result, it can be noted that in spite of a number of efforts being made, in general, there are low growth rates in industry, there is a deficit of investments in the fixed assets. Most of the investments in fixed assets are carried out at the expense of the organizations’ own funds. A significant number of economic entities do not have the means, necessary for the technological renewal. Unfortunately, the regulatory framework in the field of accounting for the fixed assets and accrual of depreciation does not imply the use of a special account for the accumulation, and, most importantly, for the purposeful control of the use of the depreciation fund.
First of all, it is necessary for companies with state participation and monopoly organizations. The lack of control over the targeted use of the depreciation fund led to a deterioration in the dynamics of indexes, characterizing the state and movement of the fixed assets, as evidenced by data on relevant indexes. Accelerated depreciation, used in tax accounting, should be monitored. However, at present, this only leads to an increase in costs. The article proposes accounting entries for the formation of an amortization fund and information on its intended use. In IFRS standards, information on the amount of accrued depreciation on fixed assets is generated in the reporting, which should also be shown in the financial statements of domestic organizations (especially with the state participation). Ambiguity in the interpretation of legislative and regulatory acts in the field of accounting for the fixed assets, accrual of depreciation and the formation of an amortization fund does not contribute to improving the investment climate in the country and leads to significant wear and tear in virtually all sectors of the economy. The article concludes that there is a significant underinvestment of the domestic economy, especially for manufacturing organizations.

Research purpose. In order to implement the optimal metropolitan governance model, it is important to understand the conditions under which this or that model is economically effective. There is a need to develop a quantitatively justified methodology for choosing the optimal metropolitan governance model for different types of metropolitan areas. It has been emphasized in some federal documents of Russia, for example, in the “Recommendations for the selection of pilot projects for approbation and improvement of mechanisms for managing the development of metropolitan areas in the Russian Federation”.
Materials and methods. Domestic researchers (N. Zubarevich, K. Gonchar, etc.) and foreign researchers (Glaeser Edward L., Nakamura, Ciccone A., Hall R., etc.) carried out the study of quantitative relationships between the economic growth of cities and the characteristics of cities.However, for metropolitan areas, the analysis of the relationship has not yet been implemented between the outpacing economic growth of the metropolitan area relative to the average country values (labor productivity and GDP per capita), the institutional factor (the type of metropolitan governance model), andthe non-institutional factor (population size).
To identify the dependencies we are interested in, we used the OECD statistical database and OECD researches to identify the metropolitan governance model in the sample of metropolitan areas in the world. The sample in this research was 87 metropolitan areas in Europe and was divided into groups, depending on the population and the introduced metropolitan governance model. For each group, a correlation-regression analysis was performed and a weighted average was calculated from the indexes of the economic growth. As the leading index of the economic growth, labor productivity was used, as the final - GDP per capita. Then a comparison was made between the real value of economic growth in each surveyed metropolitan area and the expected value when implementing different metropolitan governance model. If the comparison showed the non-optimality of the implemented model for some index of the economic growth, then the values of the economic growth in the metropolitan area and the national average were compared. As a result, a recommendationwas given for the metropolitan area on the degree of need for the management reform and an optimal metropolitan governance model was selected.
Results. Based on the revealed regularities, we have created a methodical approach to choose the optimal model of metropolitan governance according to the population size. It can be used as a tool to justify metropolitan governance reform. The advantage of the approach is the use of real quantitative data that reduces the degree of subjectivity in decision-making
Conclusion. The methodical approach is tested on the example of eightmetropolitan areas (Lublin, Palermo, Krakow, Paris, Stuttgart, Madrid, Geneva, and Linz). It was revealed that there is no metropolitan governance model, which is always more efficient for all objects. As the result of the analysis for Geneva, the degree of need for management reforms was described as “high” with a recommendation for a transition to a decentralized metropolitan governance model. For Linz, Stuttgart and Madrid, the degree of need for reform is characterized as “low” with a recommendation for a transition to decentralization (Stuttgart) and centralization (Linz and Madrid). The rest of the metropolitan areas of the sample do not need reforms.

In the period of the existence of post-soviet Russia, the health care system has remained and remains one of the most important and, at the same time, the problem element of it. We have to admit that not always medical services, offered by our state, are positive, if we consider them, for example, through the concept of “quality”. Undoubtedly, this is determined by the existing medical structure, starting with the number of different hospital establishments and ending with the degree of qualification and competence of medical specialists.
Thus, the purpose of this article is a comprehensive analysis of the healthcare system that was established in the Russian Federation in 1990–2015, the object of the study is the entire Russian health care system, and the subject is specific statistical data on the hospital beds and hospitals in Russia.
Problems of health development, as well as various methodological issues of statistical research, including the accounting of hospital facilities, hospital beds, doctors in the context of specialties, morbidity are considered in the works of both domestic and foreign scientists (V.Medic, M. Tokmachev, G. Ulumbekova, S. Banin, McKee Martin and others).
The main directions of development of the national medicine for the specified period of time, its characteristic features and problems of concern that cause dysfunction in the work of the health care protection mechanism for the citizens were identified in the context of the dynamics in such statistical indexes as the total number of hospital and outpatient clinics, hospital beds in them, the number of doctors and the state of morbidity of the population, published by the Federal State Statistics Service.
As a research task, attempts were made to assess the impact of changes in these indexes on the state of Russian health care over the period as a whole. Moreover, the work revealed the main content concepts on this topic, explained the nominal structure of the existing nomenclature, provided methodological explanations for the specifics of the changes that were taking place, and indicated the measure of the implementation of the state program “Health Development”. The tools for the study were tables and graphs of visualizing informative data, as well as various formulas that form the basis of health statistics, and analytical methods for studying the processes occurring in a given medium. Based on the results of the study, a number of specific patterns between the phenomena and indexes were identified, as well as a description of the current trends in the sphere of the Russian medicine in the context of the bed capacity for individual medical specializations, the number of hospitals and medical practitioners.

The aim of the research is to clear up the influence of examination stress on the results of completing examination papers by students in the situation of trial General and Unified State Examinations, imitating the real-life environment of unified state certification of schoolchildren. The tasks of the research included determining the dynamics of psychophysiological stress indices at different examination stages, and evaluating additional factors (the subject in which the examination is held, the strategy of solving the variant, success of solving the task etc.), influencing the quantity and quality of stress reactions at the examination.
The novelty of the research is in the attempt to overcome the problem of confusing the notions of examination stress and examination anxiety, caused by metering the students’ state either before or after the examination. The technology of online monitoring the students’ psychophysiological state is used in the work, which makes it possible to eliminate a number of restrictions occurring during subjective evaluation of the state by the students themselves. Telemetric cardiorhythmography was chosen as the basic method. The method is based on a three-component model of extreme states with consequent domination of one of the three stress-reactive systems. A cardiointervalogramm was being registered in the research process in the online mode and underwent spectral analysis. The following indices of heart rate variability were recorded in order to determine stress reactions: the total power of the spectrum (TP), the spectrum power in low-frequency (LF) and high-frequency (HF) regions, and a vegetative balance index (relation of the spectrum powers in low-frequency and high-frequency regions (LF/HF)). When the total power of the heart rate fell and, at the same time, the vegetative balance index rose, a conclusion was made of there being a stress reaction. Twenty-five students of an illustrious school were examined.
Stress reactions were already recorded when the students read the instructions, and their number increased in the process of the examination, reaching the maximum by the end of completing the work. The analysis of subjective evaluation of the state by the students themselves reveals that they often evaluate it inadequately. Significant statistical differences were found between the levels of stress at examinations in different subjects.
The highest stress level was recorded at the examination in Russian. It was revealed, that the students who chose a free strategy of completing the tasks and followed it, had fewer stress reactions than those who completed the tasks one by one. The differences in the stress levels were registered between students who got different grades: the students who were graded “good”, had the most stress reactions, those who were graded “satisfactory”, had the fewest stress reactions.
The results of the study show that the General and Unified State Examinations are highly stressful events: in average, the students were under stress about one third of the time of completing the exam tasks. The given events have a significant impact on school leavers’ psychophysiological state. Additional factors were determined that cause stress reactions at the examination.

The article deals with the problems of radiological and economic efficiency of decontamination procedures as a measure of eliminating radioactive contamination in scarcely populated residential areas of Fukushima Prefecture (Japan).
The objective of the research was to identify and compare with officially declared results the real effects of the decontamination measures on improving the radiation situation and reducing radiation doses for the population in Fukushima region. There was another objective of estimating the expected decontamination expenditure for these territories and the economic efficiency of this measure in accordance with the official international recommendations. The results of such kind of survey for Japan and actual values of the prevented doses due to the decontamination have not been published before. The key objective of this research was to assess the need for decontamination in sparsely populated areas of Fukushima Prefecture taking into account relatively low radiation background in these areas and significant associated financial losses.
The initial data for the research have been taken from the Environment Ministry (Japan) reports on the restoration progress in the NPP area. The data on the current radiation situation in Japan have been taken from the Japan Nuclear Regulatory Commission Internet publications. A mathematical modeling of the radiation situation in remediation territories near Fukushima-1 NPP was carried out in the research taking into account the simultaneous impact of several natural and anthropogenic factors. This mathematical model is described in the article. Some empirical dependencies obtained after the Chernobyl accident were also used in it.
As the results of the research, the estimated values of actual, predicted and prevented by the decontamination and the resettlement measures doses to residents in one specific Fukushima prefecture municipality were presented.
The total and average financial costs per unit of prevented exposure dose for different emergency measures scenarios were estimated, including longterm and short-term evacuation and decontamination. The estimated values of the decontamination and the resettlement effectiveness were presented based on the comparison of the public costs and benefits.
The author goes on argue that radiological effectiveness of the decontamination measures was very low. He noted that the measures were inconsistent with the principles of cost optimization in the world radiation protection standards. However, at the same time, the decontamination measures made it possible to prevent possible high costs to the government, and some positive social effects were finally achieved.

This article by Ildar F. Khasanov has been retracted (i.e. withdrawn from the press) by the editor with permission of the publisher.
Retracted article due to unformed borrowings (plagiarism).

This article by Irina P. Lotova has been retracted (i.e. withdrawn from the press) by the editor with permission of the publisher.
Retracted article due to duplicate publication.

This article by Denis A. Faleev, Sergey A. Lapshinov has been retracted (i.e. withdrawn from the press) by the editor with permission of the publisher.
Retracted article due to unformed borrowings (plagiarism).

This article by Irina A. Kiseleva, Natalya V. Gryzunova, Bui Ngoc Anh has been retracted (i.e. withdrawn from the press) by the editor with permission of the publisher.
Retracted article due to duplicate publication.

This article by Anna A. Kokorina, Darya A. Pavlutsky has been retracted (i.e. withdrawn from the press) by the editor with permission of the publisher.
Retracted article due to duplicate publication.

This article by Olga A. Mahova, Elena A. Egorova has been retracted (i.e. withdrawn from the press) by the editor with permission of the publisher.
Retracted article due to the incorrect composition of the authors and the republishing of the article without the consent of the author.