<!DOCTYPE article PUBLIC "-//NLM//DTD JATS (Z39.96) Journal Archiving and Interchange DTD v1.0 20120330//EN" "JATS-archivearticle1.dtd">
<article xmlns:xlink="http://www.w3.org/1999/xlink">
  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>Methodology For Environmental Methods of Mathematical Modeling</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Nadiia Bielikova</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Daniil Shmatkov</string-name>
          <email>d.shmatkov@gmail.com</email>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Research Centre for Industrial Problems of Development of the National Academy of Sciences of Ukraine</institution>
          , І
          <addr-line>nzhenerny lane, 1, A, Kharkiv, 61166</addr-line>
          ,
          <country country="UA">Ukraine</country>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>Scientific and Research Institute of Providing Legal Framework for the Innovative Development of the National Academy of Legal Sciences of Ukraine</institution>
          ,
          <addr-line>Chernyshevskaya st., 80, Kharkiv, 61002</addr-line>
          ,
          <country country="UA">Ukraine</country>
        </aff>
      </contrib-group>
      <abstract>
        <p>The article is aimed at developing methodological support for environmental monitoring using modeling methods, which will optimize the number of studied indicators and facilitate the processing, interpretation and visualization of the results. Developed methodology envisages the following stages: formation of the initial set of partial indicators; factor analysis of partial indicators and reduction of those with a factor load of less than 60%; structuring a set of partial indicators (selection of components and calculation of integrated indicators); application of matrix analysis for grouping of monitoring objects.</p>
      </abstract>
      <kwd-group>
        <kwd>1 Environmental monitoring</kwd>
        <kwd>sustainable development</kwd>
        <kwd>modeling</kwd>
        <kwd>factor analysis</kwd>
        <kwd>integral indicator</kwd>
        <kwd>partial indicators</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1. Introduction</title>
      <p>Sustainable development involves the
harmonization of development and functioning of
environmental, economic, and social areas. The
interaction between these areas is embodied in the
formation of the outline of direct and indirect
relation between the supervision and dynamics of
their development and the results achieved. The
problem of sustainable development is complex,
as part of its solution it is advisable to monitor the
economy, social area, and the state of the
environment using methods that would take into
account the complexity and difficult predictability
of this process.</p>
      <p>ICT play a significant role in the
transformation of sustainable development
approaches. Issues of organization and
digitalization of monitoring the functioning of
certain areas of sustainable development, of large
amounts of information (variety baselines), of the
complexity of their processing and interpretation
of results, and of the formulation of conclusions
require knowledge-intensive approaches.</p>
      <p>This article is aimed at developing
methodological support for environmental
monitoring using modeling methods, which
optimize the number of studied indicators and
facilitate the processing, interpretation and
visualization of the results.</p>
    </sec>
    <sec id="sec-2">
      <title>2. Methodology</title>
      <p>Ensuring environmental monitoring within the
developed methodology envisages the following
stages: formation of the initial set of partial
indicators; factor analysis of partial indicators and
reduction of those with a factor load of less than
60%; structuring a set of partial indicators
(selection of components and calculation
of
integrated
indicators);
application
of
matrix
analysis for grouping of monitoring objects.</p>
      <p>
        As the initial set of monitoring indicators is
large, in conditions of insufficient time it is
advisable to use methods of data reduction [
        <xref ref-type="bibr" rid="ref1">1</xref>
        ].
One of such methods is the factor analysis which
is widely applied in ecological science in various
directions [
        <xref ref-type="bibr" rid="ref2 ref3 ref4 ref5">2–5</xref>
        ].
      </p>
      <p>Within
the
framework of the
proposed
approach, the first stage determines the number of
factors that should be identified
within the
reduction of monitoring indicators. The initial set
of partial indicators takes part in the analysis.</p>
      <p>The essence of the analysis is that during the
sequential selection of factors, they include less
and less variability of monitoring indicators.
Therefore, the decision on when to stop the
procedure for the selection of factors depends
largely on the analysis purposes, but one of the
recommendations to streamline the process of
selecting the number of factors is to consider the
scree plot.</p>
      <p>Next, it is proposed to structure the initial set
of indicators for monitoring, which remained after
the factor analysis.</p>
      <sec id="sec-2-1">
        <title>Structuring is done by identifying the components that will be followed by a generalized assessment of the environment.</title>
        <p>All selected components correspond to the main
components
of the
living
environment for
monitoring of which the initial set was formed and
which includes the following indicators:
– integral indicator of the atmosphere
I – integral indicator of the water resources
IA
W
S
I
Ws
F
I</p>
        <p>NR
assessment;
assessment;
assessment;
assessment;</p>
        <p>I – integral indicator of the soil assessment;
– integral indicator of the wastes
I – integral indicator of the forest resources
– integral indicator of the nature reserves
and hunting grounds assessment.</p>
        <p>
          To calculate the integrated components of the
above indicators, it is proposed to use the entropy
method [
          <xref ref-type="bibr" rid="ref6">6</xref>
          ], the stages of which (adapted to the
objectives of the environmental monitoring) are
the formation of a set of partial indicators and
their
assessment,
standardization
of
partial
indicators taking into account their impact on the
environment, and calculation of the value of
entropy of the environment features and integral
indicators for estimation of its components.
        </p>
        <p>
          This approach allows us to take into account
that the greater the entropy of any partial indicator
that characterizes a
certain
feature
of any
component
of
the
environment,
the
more
disordered the ecological system would be as a
whole. If the entropy of the trait, expressed as a
partial exponent, is insignificant, then its weight
in the total set of traits is also insignificant [
          <xref ref-type="bibr" rid="ref6">6</xref>
          ]:
 (  ) = ∑     ,     = 1,  ,
(1)

 =1
where  (  ) – integral value of the object;
  – the entropy of j-th feature;
  – quantitative assessment of j-th feature of i
object;
m – number of objects;
n – number of features.
        </p>
        <p>Matrix analysis is used in this work to
visualize
the
results
of
monitoring
which
facilitates their interpretation and the possibility
of obtaining homogeneous groups of objects of
the
study
by positioning them
in different
quadrants of matrices. Having a group of objects
in the study</p>
        <p>we can isolate their common
characteristics. To do this, we offer three matrices
or positioning planes:
•
•
•</p>
        <p>Atmosphere – Water resources (IA – IW).</p>
      </sec>
      <sec id="sec-2-2">
        <title>Soil – Wastes (IS – IWs).</title>
        <p>Forest resources – Nature reserves and
hunting grounds (IF – INR).</p>
        <p>Accordingly, the axes of these matrices are
integrated indicators for assessing the six selected
components of the environment.</p>
        <p>To determine the boundaries of the quadrants
of the</p>
        <p>matrices, the range of values of the
integrated indicators for environment components
estimation can be divided into three parts by the
golden
ratio.</p>
        <p>
          The
golden
ratio
is such a
proportional division of a segment into unequal
parts in which the whole segment belongs to the
larger part as much as the largest part belongs to
the smaller one; or in other words, the smaller
segment refers to the larger as the larger segment
refers to all [
          <xref ref-type="bibr" rid="ref7">7</xref>
          ]:
where YB, AB, YA – parts of a segment or
numerical series.
        </p>
        <p>
          Depending on the defined conditions and
features of research objects development, as well
as properties and role which they carry out in a
system, nine functions of distribution of the
investigated sample are allocated: chaos,
development of elements, development of
properties, development of relations, balance of
functions of development and preservation,
preservation of relations, preservation of
properties, preservation of elements, and collapse
[
          <xref ref-type="bibr" rid="ref7 ref9">7,9</xref>
          ]. Environmental monitoring objects can be
considered as systems with connections and
elements. Since the development of this system is
unbalanced, in certain periods of time it even
contains signs of chaos, the most suitable function
to describe these processes can be defined as
“development of elements” with the appropriate
percentage distribution of parts of the range of
values: [0,0; 0,328) – low, (0,329; 0,735) –
medium level, (0,736; 1,0) – high level].
        </p>
      </sec>
    </sec>
    <sec id="sec-3">
      <title>3. Results</title>
      <p>At the first stage we formed an initial set of
partial indicators for assessing the ecological
sphere of sustainable development of the country
– its environment.</p>
      <p>The environment has the following main
components that affect health and quality of life:
air, water, soil, wastes, forests, nature reserves and
hunting, etc. These components are reflected both
in international indices that assess various aspects
of habitat quality and in statistics to assess the
development of regional environments. Based on
this, it is proposed to monitor the environment
using the following partial indicators (Table 1).</p>
      <p>Partial indicators
Wastewater treatment facilities,
million m3
Application of mineral fertilizers per
hectare of acreage, kg
Application of organic fertilizers per
hectare of acreage, tons
The area of crops fertilized with
mineral fertilizers, thousand
hectares
The area of crops fertilized with
organic fertilizers, thousand
hectares
Areas where pesticides were used,
thousand hectares
Waste generation, thousand tons
Waste generation of I–III classes of
danger, thousand tons
Waste generation per square
kilometer, tons
Waste generation per capita, kg
Waste disposal, thousand tons
Utilization of wastes of I–III classes of
danger, thousand tons
Waste incineration, thousand tons
Waste disposal in dedicated places
and facilities, thousand tons
Removal of waste of I-III classes of
danger in specially designated places
and facilities, thousand tons
Waste disposal in fly-tipping,
thousand tons
Total amount of waste accumulated
during operation in waste disposal
sites, thousand tons
Total amount of waste accumulated
during operation in waste disposal
sites per square kilometer, thousand
tons
Total amount of waste accumulated
during operation in waste disposal
sites per person, thousand tons
Area of forest destruction, hectares
Number of forest fires, units
The area of forest lands covered by
fires, hectare
Area of burned and damaged forest,
m3
Area of reforestation, hectares
Area of afforestation, hectares
Area of transfer of forest areas of
natural regeneration into land
covered with forest vegetation,
hectares
n.51
n.52
n.53
n.54
n.55
n.56
n.57</p>
      <p>Partial indicators
Area of transfer of forest areas into
land covered with forest vegetation,
hectares
Number of illegal felling, units
Damage caused to forestry, millions
of Ukrainian hryvnia
The area of hunting lands provided
for use, thousand hectares
Land area of nature reserves,
biosphere reserves and national
nature parks, hectares
Number of wild animals (ungulates)
by objects on the territory of which
the lands are located, thousand
heads
Number of wild animals (fur animals)
by objects on the territory of which
lands are located, thousand heads
Number of wild animals (game birds)
by objects on the territory of which
the lands are located, thousand
heads</p>
      <p>The composition of environmental monitoring
objects may vary and depends on the objectives.
In particular, it can be conducted at the global and
national levels: for countries, regions, cities or
other territories and settlements.</p>
      <p>In this article, the objects of monitoring are
defined as regions (administrative-territorial
units) of Ukraine which have different
characteristics of the environment due to different
levels of industrial development, climate,
geographical location, state of natural resources,
and other factors.</p>
      <p>Data collection of partial indicators for
environmental monitoring in statistical sources
allowed us to establish that the objects of
monitoring have significant differences in the
values of partial indicators n.1 – n.57. For
example, the discrepancy between the maximum
(233,7 thousand tons in the Donetsk region) and
the minimum (0,2 thousand tons in the
Transcarpathian region) values of sulfur dioxide
emissions into the air was 1168,5 times (Table 2).
Volyn region
Dnipropetrovsk region
Donetsk region
Zhytomyr region
Transcarpathian region
Zaporizhya region
Ivano-Frankivsk region
Kyiv region
Kirovograd region
Luhansk region
Lviv region
Mykolayiv region
Odessa region
Poltava region
Rivne region
Sumy region
Ternopil region
Kharkiv region
Kherson region
Khmelnytsky region
Cherkasy region
Chernivtsi region
Chernihiv region
1,4 0,4 0,5
86,5 66,8 31,2
76,2 233,7 44,8
2,7 1,0 1,6
0,4 0,2 0,7
13,1 79 31,9
37,3 129,6 14,5
12,4 14,3 4,8
4,0 0,9 1,4
10,4 33,3 8,1
8,4 39,8 6,8
3,6 0,7 2,6
3,6 1,9 2,4
6,3 7,4 10
2,6 0,6 2,8
3,5 3,1 3,2
1,5 0,3 1
6,5 11,3 7,8
1,2 0,7 0,3
2,8 2,5 5,3
8,8 5,0 10
0,9 0,4 0,3
3,9 6,4 3,6</p>
      <p>Consideration of the scree plot (Fig. 2) allows
a researcher to determine the place where the
decline in the eigenvalues of the factors from left
to right is slowed down as much as possible. In
this graph, this place corresponds to the number
of factors equal to six. But the maximum
variability of the initial indicators is explained by
the first and second factors (Table 3).</p>
      <p>As can be seen from table 3, the first and
second factors explain 49,83%, i.e. half of the
variance of the initial indicators of environmental
monitoring, and all six factors – 77,92% of the
total variance. Therefore, in the process of factor
analysis, it is possible to identify either two main
factors (factor 1 and factor 2) and to reduce those
indicators of environmental monitoring that are
not included in their composition or to identify six
factors and to reduce those indicators of
environmental monitoring that are not included in
their composition.</p>
      <p>Leaving for analysis factors 1 and 2 and
reducing the indicators of environmental
monitoring which have a factor load of more than
60% and explain 49,83% of the total variance, the
following results were obtained:
• Composition of factor 1 “Dangerous”:
n.1, n.2, n.3, n.4, n.5, n.6, n.7, n.8, n.11, n.18,
n.19, n.20, n.21, n.22, n.24, n.33, n.34, n.35,
n.37, n.40, n.41, n.42.
• Composition of factor 1 “Permissible”:
n.12, n.13, n.15, n.16, n.25, n.44, n.45, n.46,
n.47, n.49, n.51, n.55, n.56.</p>
      <p>Thus, factor 1 includes monitoring indicators
that characterize the negative phenomena of the
environment: emissions of hazardous substances
into the atmosphere, different types of waste
generation, etc. Given the composition of the
indicators that fall into factor 1, it can be called
“Dangerous” because it has a negative impact on
the environment.</p>
      <p>Factor 2 includes monitoring indicators that
characterize less dangerous phenomena: water
intake and its use for various purposes, application
of mineral fertilizers to soil, etc. Given the
composition of the indicators of factor 2, it can be
conditionally called "Permissible" because it has
a permissible and, in some cases, positive impact
on the environment.</p>
      <p>According to the criterion of factor load less
than 60%, the following indicators were reduced:
n.9., N.10, n.14, n.17, n.23, n.26, n.27, n.28, n.29,
n.31, n.32, n.36, n.38, n.39, n.43, n.48, n.50, n.52,
n.53, n.54, n.57.</p>
      <p>The six selected factors include indicators that
characterize areas of environmental monitoring
such as air and water pollution by various types of
hazardous substances (factor 1 and factor 3);
wastes management (factor 3); use of natural
resources for different purposes (factor 2);
restoration of forest resources (factor 4); soil
management (factor 5); loss of forest stands
(factor 6).</p>
      <p>Factors 1–3 were the largest in terms of the
number of included indicators, and only one
indicator was included in factor 6, which
corresponds to the general rule of factor analysis
– reduction of the number of indicators included
in each subsequent selected factor due to reduced
variability of indicators.</p>
      <p>The analysis allowed us to conclude that the
minimum number of factors that can be identified
is two factors, and the maximum is six factors.
And in addition, the logic of this study allowed us
to recommend the second option of factor analysis
according to which there are six factors
influencing the environment which explain the
maximum indicators variability.</p>
      <p>Thus, as a result of the reduction, the initial set
of environmental monitoring indicators was
reduced from 57 to 45.</p>
      <p>After calculating the entropy of integrated
indicators that characterize the state of the
selected components of the environment (Fig. 1),
we carried out the positioning of monitoring
objects in three matrices, for example, the matrix
“Soil–Wastes” is presented in Fig. 2.</p>
      <p>Characteristics of matrix quadrants are the
following:</p>
      <p>HH – high assessment of soil – high level of
wastes management;</p>
      <p>HM – high assessment of soil – medium level
of wastes management;</p>
      <p>HL – high assessment of soil – low level of
wastes management;</p>
      <p>MH – medium assessment of soil – high level
of wastes management;</p>
      <p>MM – medium assessment of soil – medium
level of wastes management;</p>
      <p>ML – medium assessment of soil – low level
of wastes management;</p>
      <p>LH – low assessment of soils – high level of
wastes management;</p>
      <p>LM – low assessment of soil – medium level
of wastes management;</p>
      <p>LL – low assessment of soil – low level of
wastes management.</p>
      <p>Coordinates of positioning points in the matrix
are the following: Ukraine (0,371; 0,735);
Vinnytsia region (0,134; 0,773); Volyn region
(0,623; 0,775); Dnipropetrovsk region (0,144;
0,234); Donetsk region (0,384; 0,710); Zhytomyr
region (0,462; 0,777); Transcarpathian region
(0,707; 0,776); Zaporizhzhya region (0,109;
0,761); Ivano-Frankivsk region (0,671; 0,769);
Kyiv region (0,574; 0,772); Kirovograd region
(0,072; 0,639); Luhansk region (0,392; 0,769);
Lviv region (0,571; 0,764); Mykolayiv region
(0,241; 0,762); Odessa region (0,072; 0,775);
Poltava region (0,321; 0,686); Rivne region
(0,710; 0,775); Sumy region (0,215; 0,738);
Ternopil (0,469; 0,776); Kharkiv (0,070; 0,740);
Kherson region (0,352; 0,761); Khmelnytsky
region (0,354; 0,774); Cherkasy region (0,362;
0,776); Chernivtsi region (0,658; 0,777);
Chernihiv region (0,230; 0,775).</p>
      <p>The quadrants that are on the line of
development of monitoring objects from the worst
to the best condition are Dnipropetrovsk,
Donetsk, and Rivne regions.</p>
    </sec>
    <sec id="sec-4">
      <title>4. Conclusions</title>
      <p>The given methodology for environmental
monitoring with use of methods of mathematical
modeling allows a researcher to draw conclusions
with regard to a habitat condition as a whole in the
country, to define the most dangerous state of
HH
HM</p>
      <p>HL
ecology according to its administrative units, and
to analyze results of an environment condition
assessment according to its components.</p>
      <p>The proposed methodology support provides
the implementation of the complex approach to
the establishment of monitoring of an ecological
component of sustainable development and to
strengthen its scientific substantiation. Its
advantage is the ease and high implementation
opportunities through ICT tools to reduce the time
of monitoring and systematic analysis for clear
conclusions and recommendations for more
effective implementation of the concept of
sustainable development.</p>
    </sec>
    <sec id="sec-5">
      <title>5. References</title>
    </sec>
  </body>
  <back>
    <ref-list>
      <ref id="ref1">
        <mixed-citation>
          [1]
          <string-name>
            <given-names>D.</given-names>
            <surname>Shmatkov</surname>
          </string-name>
          ,
          <string-name>
            <given-names>N.</given-names>
            <surname>Bielikova</surname>
          </string-name>
          ,
          <string-name>
            <given-names>N.</given-names>
            <surname>Antonenko</surname>
          </string-name>
          ,
          <string-name>
            <given-names>O.</given-names>
            <surname>Shelkovyj</surname>
          </string-name>
          ,
          <article-title>Developing an environmental monitoring program based on the principles of didactic reduction</article-title>
          ,
          <source>European Journal of Geography</source>
          , volume
          <volume>10</volume>
          , number 1,
          <year>2019</year>
          ,
          <fpage>99</fpage>
          -
          <lpage>116</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref2">
        <mixed-citation>
          [2]
          <string-name>
            <given-names>A.</given-names>
            <surname>Deraemaeker</surname>
          </string-name>
          ,
          <string-name>
            <given-names>K.</given-names>
            <surname>Worden</surname>
          </string-name>
          ,
          <article-title>A comparison of linear approaches to filter out environmental effects in structural health monitoring</article-title>
          ,
          <source>Mechanical systems and signal processing</source>
          , volume
          <volume>105</volume>
          ,
          <year>2018</year>
          ,
          <fpage>1</fpage>
          -
          <lpage>15</lpage>
          . https://doi.org/10.1016/j.ymssp.
          <year>2017</year>
          .
          <volume>11</volume>
          .045
        </mixed-citation>
      </ref>
      <ref id="ref3">
        <mixed-citation>
          [3]
          <string-name>
            <given-names>M. S.</given-names>
            <surname>Guerreiro</surname>
          </string-name>
          ,
          <string-name>
            <given-names>I. M.</given-names>
            <surname>Abreu</surname>
          </string-name>
          , Á. Monteiro,
          <string-name>
            <given-names>T.</given-names>
            <surname>Jesus</surname>
          </string-name>
          ,
          <string-name>
            <surname>A. Fonseca,</surname>
          </string-name>
          <article-title>Considerations on the monitoring of water quality in urban streams: a case study in Portugal, Environmental monitoring and assessment</article-title>
          , volume
          <volume>192</volume>
          ,
          <year>2020</year>
          ,
          <fpage>1</fpage>
          -
          <lpage>11</lpage>
          . https://doi.org/10.1007/s10661- 020-8245-y
        </mixed-citation>
      </ref>
      <ref id="ref4">
        <mixed-citation>
          [4]
          <string-name>
            <given-names>A. H.</given-names>
            <surname>Hirzel</surname>
          </string-name>
          ,
          <string-name>
            <given-names>J.</given-names>
            <surname>Hausser</surname>
          </string-name>
          ,
          <string-name>
            <given-names>D.</given-names>
            <surname>Chessel</surname>
          </string-name>
          ,
          <string-name>
            <given-names>N.</given-names>
            <surname>Perrin</surname>
          </string-name>
          ,
          <article-title>Ecological‐niche factor analysis: how to compute habitat‐suitability maps without absence data?</article-title>
          ,
          <source>Ecology</source>
          , volume
          <volume>83</volume>
          , number 7,
          <year>2002</year>
          ,
          <fpage>2027</fpage>
          -
          <lpage>2036</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref5">
        <mixed-citation>
          [5]
          <string-name>
            <given-names>O.</given-names>
            <surname>Ovaskainen</surname>
          </string-name>
          ,
          <string-name>
            <given-names>G.</given-names>
            <surname>Tikhonov</surname>
          </string-name>
          ,
          <string-name>
            <given-names>A.</given-names>
            <surname>Norberg</surname>
          </string-name>
          ,
          <string-name>
            <given-names>F.</given-names>
            <surname>Guillaume Blanchet</surname>
          </string-name>
          ,
          <string-name>
            <given-names>L.</given-names>
            <surname>Duan</surname>
          </string-name>
          ,
          <string-name>
            <given-names>D.</given-names>
            <surname>Dunson</surname>
          </string-name>
          ,
          <string-name>
            <given-names>T.</given-names>
            <surname>Roslin</surname>
          </string-name>
          ,
          <string-name>
            <given-names>N.</given-names>
            <surname>Abrego</surname>
          </string-name>
          ,
          <article-title>How to make more out of community data? A conceptual framework and its implementation as models and software, Ecology letters</article-title>
          , volume
          <volume>20</volume>
          , issue 5,
          <year>2017</year>
          ,
          <fpage>561</fpage>
          -
          <lpage>576</lpage>
          . https://doi.org/10.1111/ele.12757
        </mixed-citation>
      </ref>
      <ref id="ref6">
        <mixed-citation>
          [6]
          <string-name>
            <surname>Infocommunications</surname>
          </string-name>
          .
          <article-title>Science and Technology</article-title>
          .
          <source>IEEE PIC S&amp;T 2015</source>
          . pp.
          <fpage>269</fpage>
          -
          <lpage>271</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref7">
        <mixed-citation>
          [7]
          <string-name>
            <given-names>V. Y.</given-names>
            <surname>Vasylev</surname>
          </string-name>
          ,
          <string-name>
            <given-names>V. V.</given-names>
            <surname>Krasylnykov</surname>
          </string-name>
          ,
          <string-name>
            <given-names>S. Y.</given-names>
            <surname>Plaksyi</surname>
          </string-name>
          ,
          <string-name>
            <given-names>T. N.</given-names>
            <surname>Tiahunova</surname>
          </string-name>
          ,
          <article-title>Statistical analysis of multidimensional objects of arbitrary nature</article-title>
          , Moscow, YKAR,
          <year>2004</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref8">
        <mixed-citation>
          [8]
          <string-name>
            <given-names>N. N.</given-names>
            <surname>Moiseev</surname>
          </string-name>
          ,
          <string-name>
            <given-names>E. P.</given-names>
            <surname>Ivanilov</surname>
          </string-name>
          ,
          <string-name>
            <given-names>E. M.</given-names>
            <surname>Stolyarova</surname>
          </string-name>
          , Optimization methods, Moscow, The science,
          <year>1978</year>
          .
        </mixed-citation>
      </ref>
      <ref id="ref9">
        <mixed-citation>
          [9]
          <string-name>
            <given-names>O. M.</given-names>
            <surname>Prokopenko</surname>
          </string-name>
          (Ed.)
          <article-title>Statistical data Environment of Ukraine for 2017, Kyiv</article-title>
          , State Statistics Service of Ukraine,
          <year>2018</year>
          .
        </mixed-citation>
      </ref>
    </ref-list>
  </back>
</article>