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  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>COVID-19 Cases</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Vitaliy Yakovyna</string-name>
          <email>yakovyna@matman.uwm.edu.pl</email>
          <xref ref-type="aff" rid="aff0">0</xref>
          <xref ref-type="aff" rid="aff2">2</xref>
          <xref ref-type="aff" rid="aff3">3</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Natalya Shakhovska</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Khrystyna Shakhovska</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Jaime Campos</string-name>
          <email>jaime.campos@lnu.se</email>
          <xref ref-type="aff" rid="aff0">0</xref>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>World</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Health</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>COVID-19, Machine Learning</institution>
          ,
          <addr-line>Regression Tree, Clustering, Prediction</addr-line>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>Linnaeus University</institution>
          ,
          <addr-line>PG Vejdes 6 &amp; 7, Växjö, SE-35195</addr-line>
          ,
          <country country="SE">Sweden</country>
        </aff>
        <aff id="aff2">
          <label>2</label>
          <institution>Lviv Polytechnic National University</institution>
          ,
          <addr-line>12 Bandera str., Lviv, 79013</addr-line>
          ,
          <country country="UA">Ukraine</country>
        </aff>
        <aff id="aff3">
          <label>3</label>
          <institution>University of Warmia and Mazury in Olsztyn</institution>
          ,
          <addr-line>2 Michała Oczapowskiego str., Olsztyn, 10-719</addr-line>
          ,
          <country country="PL">Poland</country>
        </aff>
      </contrib-group>
      <abstract>
        <p>The COVID-19 pandemic is having an unprecedented impact on society and the economy, affecting virtually every aspect of people's daily life and all sectors of the economy. In this situation, society and the health care system need help from modern technologies such as Artificial Intelligence, Big Data, and Machine Learning, which intended to help governments to choose and implement an adequate strategy to combat the spread of the disease by balancing between human safety and the constraints of social and economic life. This paper considers the recommendation rules extracted from the novel ensemble of machine learning methods such as regression tree and clustering. The merged Oxford COVID-19 Government Response Tracker and European Centre for Disease Prevention and Control Covid-19 Cases datasets have been used with the data ranged from January 01 to October 04, 2020. The conclusions and findings of the study could be helpful for decision making on appropriated state policy for reducing the spread of new Covid-19 cases.</p>
      </abstract>
      <kwd-group>
        <kwd>Keywords1</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1. Introduction</title>
      <p>
        2020 Copyright for this paper by its authors.
(iii) how many people in general will be affected by the disease [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ]. The most reliable and reasoned
answers to such questions will help governments to choose and implement an adequate strategy to
combat the spread of the disease by balancing between human safety and the constraints of social and
economic life.
      </p>
      <p>In this situation, society and the health care system need help from modern technologies such as
Artificial Intelligence (AI), Big Data, and Machine Learning to fight new diseases and make rapid
progress. Governments and health organizations need effective decision support systems during a
pandemic to effectively control the virus and make optimal real-time decisions to curb the spread of
the disease. Artificial intelligence systems and methods can also provide significant assistance in the
development of the COVID-19 vaccine. AI methods and algorithms are used to analyze the spread of
the disease, predict and track patients and potential carriers of infection. Intelligent analysis of data on
confirmed cases of illness, recovery and death is carried out.</p>
      <p>At present, the vaccine against COVID-19 is still undergoing clinical trials, and there is no proven
effective cure for this disease. In such circumstances, the only effective way to slow the spread of
infection is "social distancing" and the use of antiseptics and personal protective equipment to prevent
the transmission of the virus from person to person. At the same time, the role of modeling and
predicting the spread of the disease, the time and duration of the maximum number of infections and
the scale of the epidemic for each country is growing. The findings of such modeling and forecasting
are the basis for sound public health decisions regarding appropriate measures and the allocation of
resources, such as pulmonary ventilation systems or additional field hospitals.</p>
      <p>Behavior analysis of COVID-19 requires the development of a powerful mathematical apparatus
for tracking, including automated, its dissemination to develop timely, dynamic, and sound solutions.
As shown above, the methods and tools of artificial intelligence and machine learning are an adequate
and effective basis for such tasks. The current COVID-19 pandemic poses serious challenges for data
scientists and AI professionals due to limited and incomplete data and the large amount of
heterogeneous data, as well as the significant impact of various factors on disease behavior and
spread.</p>
      <p>The purpose of the paper is to build the recommendation rules for appropriated state policy for
reducing the spread of new Covid-19 cases. The system of these rules is based on novel ensemble of
machine learning methods such as regression tree and clustering.</p>
    </sec>
    <sec id="sec-2">
      <title>2. Related Works</title>
      <p>
        The significant impact of the COVID-19 pandemic on all spheres of public life has led researchers
to a significant interest in modeling the spread, behavior and origin of the virus, understanding its
nature and properties, and finding ways to control the disease. Since the beginning of 2020, tens of
thousands of articles have been published in various fields of science on the COVID-19 pandemic.
Research institutions, foundations and governments are investing significant human, financial and
technical resources to gain new knowledge about the pandemic and close gaps in understanding the
nature of the disease and its consequences, including medical, social, and economic. Thus, a
largescale study and analysis of publications on COVID-19 using machine learning methods by A. Doanvo
et al. [
        <xref ref-type="bibr" rid="ref4">4</xref>
        ] showed that the main volume of articles falls on research in the field of public health,
pandemic, clinical diagnosis and treatment of coronavirus. At the same time, a small amount of work
has been published on the microbiological details of this virus, including its pathogenesis and routes
of transmission. A detailed review of the literature on the application of machine and in-depth
learning algorithms in the processing of medical images for the diagnosis of coronavirus disease was
conducted in [
        <xref ref-type="bibr" rid="ref5">5</xref>
        ] together with a comparative analysis of the application of each algorithm and its
performance.
      </p>
      <p>
        The development of new effective models for predicting the number and dynamics of new
COVID-19 infections, as well as epidemiological forecasting in general, is extremely important for
the health care system, as it enables effective planning to eliminate or reduce possible epidemics. The
main requirement for such models is the maximum possible accuracy and reliability of the forecast of
epidemiological time series. To meet these requirements, a number of AI-based models have been
used for a number of years [
        <xref ref-type="bibr" rid="ref6 ref7 ref8">6–8</xref>
        ]. The methods used to solve the problem of constructing the
COVID19 prediction model have ranged from statistical autoregression like ARIMA to more robust machine
learning methods [
        <xref ref-type="bibr" rid="ref10 ref11 ref3 ref9">3, 9–11, 13–19</xref>
        ].
      </p>
      <p>
        Thus, Ribiero et al. [
        <xref ref-type="bibr" rid="ref9">9</xref>
        ] consider different regression-based models like cubist, ridge, reference
vector regressions, ARIMA along with random forest, and ensemble overlay training for one, three,
and six days prediction of cumulative value of COVID-19 cases in Brazil. They demonstrate that, in
most cases, support vector regression and stack ensemble training perform better against the accepted
criteria than the other models studied. In general, the models developed in [
        <xref ref-type="bibr" rid="ref9">9</xref>
        ] can generate accurate
forecasts with an error of less than 6.90%. In [
        <xref ref-type="bibr" rid="ref9">9</xref>
        ], it was concluded that further improvement in the
development of COVID-19 prediction models can be achieved by combining deep learning and
ensemble learning accumulation, by using multi-objective optimization for tuning the
hyperparameters of prediction models and adopting a set of features that allows to explain the
dependencies of future COVID-19 cases.
      </p>
      <p>
        Zhang et al. [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ] used a segmented Poisson model for prediction and analysis the time-series of the
COVID-19 cases in six G7 countries. In the developed model, they included government
interventions (advice/orders regarding staying at home, social distancing, blocking, and quarantine) as
factors influencing the COVID-19 outbreak. The analysis makes it possible [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ] to forecast statistically
the tipping point, duration, and intensity of attacks for the countries under study. The paper [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ]
implies that if there were no serious coercive measures against control strategies like blocking,
distancing, orders to stay at home, then the virus would spread exponentially. This indicates that the
interventions/actions have significantly reduced the size of outbreaks and flattened the epidemic curves.
      </p>
      <p>
        The dynamics of the COVID-2019 outbreak in China, Italy and France in January–March 2020 is
analyzed in [
        <xref ref-type="bibr" rid="ref10">10</xref>
        ]. Some universal epidemic spread was revealed based on the analysis of simple daily
lag maps, that allows the authors [10[ to suggest that such simple models can be successfully used to
quantify the spread of the epidemic, in particular the height and peak times of infected persons. The
authors [
        <xref ref-type="bibr" rid="ref10">10</xref>
        ] carried out the analysis of the same dataset using a susceptible-infected-recovered-deaths
model, and conclude that the parameter describing the patient recovery rate appears to be almost the
same in all countries studied, while mortality and infection rates seems to be more volatile. However,
Fanelli and Piazza [
        <xref ref-type="bibr" rid="ref10">10</xref>
        ] showed that it is necessary to reduce the infection rate sharply and quickly in
order to see a noticeable decrease in the mortality rate and epidemic peak position.
      </p>
      <p>
        Roosa et al. [
        <xref ref-type="bibr" rid="ref11">11</xref>
        ] exploited phenomenological models tested during previous outbreaks to evaluate
short-term predictions of the total number of confirmed COVID-19 cases in Hubei Province, and
separately for all other territory of China. They provide forecasts for 5, 10 and 15 days for five
consecutive days, from 5 to 9 February 2020, with quantitative uncertainty based on the generalized
model of logistical growth, the Richards growth model and the subepidemic wave model.
      </p>
      <p>
        Vaishya et al. [
        <xref ref-type="bibr" rid="ref12">12</xref>
        ] conducted a detailed analysis of publications on the use of AI for the
COVID19 pandemic. The main AI applications in the COVID-19 pandemic have been shown to include, but
not be limited to: diagnosis and early detection, patient treatment monitoring, tracking of infected
persons, disease and mortality prediction, drug and vaccine development, reducing the burden on
health workers and, finally, disease prevention. Thus, it is concluded in [
        <xref ref-type="bibr" rid="ref12">12</xref>
        ] that AI-based systems
can be effectively used for early diagnosis and treatment of patients, in decision support systems in
the medical field, as well as for training physicians and medical students on the COVID-19 disease,
which will have an impact on the strategy and tactics of treatment of subsequent patients, and thus
reduce the burden on medical staff in hospitals during a pandemic. AI technology can be useful for
tracking potential ways of spreading the virus and informing the public about the threat of the disease
through tracking the contacts of people with a confirmed diagnosis, including social platforms and
networks. Among other things, machine learning models can predict the number and dynamics of
COVID-19 incidence by region, age, social and other populations, thus helping to identify the most
vulnerable areas and segments of the population. With the ability to analyze and process data in real
time, AI can provide timely and up-to-date information to help prevent further spread of the infection.
It can be used to predict the dynamics and direction of the disease, the dynamics of the number of
diagnosed and severe cases in each region, to predict in advance the need for hospital beds, staff,
medication during the crisis. In general, AI will play an increasing role in medicine and medical
applications by providing proactive and prognostic measures in the field of health care [
        <xref ref-type="bibr" rid="ref12">12</xref>
        ].
      </p>
      <p>Basu and Campbell [13] propose a model based on Long Short-Term Memory, which was trained
on cumulative number of COVID-19 cases and deaths separately. They train the developed model
using the dataset containing number of confirmed COVID-19 cases during the period of more than
four months. The parameters of the proposed model can be adjusted in such a way as to provide the
required forecasting accuracy. In the article [13] using the developed LSTM-model, a quantitative
assessment and analysis of the impact of measures taken by various US counties on the spread of the
disease has been carried out.</p>
      <p>Neher et al. [14] consider a seasonal model based on a susceptible-infectious-recovered approach
to analyze and predict the spread of COVID-19 virus reinfection in the world in the coming years. In
their model, they consider such factors as the rate of infection, the volume and speed of emigration
and population movement, and so on. An updated version of their model [15] aims to analyze and
forecast the necessary hospital resources to combat pandemics of such a scale as COVID-19.</p>
      <p>Hu et al. [16] built and investigated a machine learning model based on composite autoencoders to
describe the spread of coronavirus in China in April 2020 based on data from previous periods. They
clustered cities and provinces based on the characteristics obtained from the developed auto-coding
model. Similar LSTM-based models have been used to study patient-related statistics [17], as well as
to identify trends in the spread of the epidemic in China [18].</p>
      <p>The study by S. Tuli et al. [19] is based on an improved machine learning model for analyzing and
predicting the spread of the COVID-19 epidemic in different countries. The authors of [19] have
developed and studied the Robust Weibull model with iterative weighting. They conclude that the
developed Weibull model is statistically better than the Gaussian baseline model for prediction of the
COVID-19 outbreak. It was shown [19] that simple Gaussian model results in an overly optimistic
COVID-19 spreading scenario. The developed model was deployed on a cloud computing platform
using the FogBus framework for more accurate and realistic forecasting of the epidemic's growth
dynamics.</p>
    </sec>
    <sec id="sec-3">
      <title>3. Material and Methods</title>
    </sec>
    <sec id="sec-4">
      <title>3.1. Dataset Description</title>
      <p>In this study we have used data from the Oxford COVID-19 Government Response Tracker as
well as European Centre for Disease Prevention and Control (ECDC) Covid-19 Cases [20].</p>
      <p>The Oxford COVID-19 Government Response Tracker (OxCGRT) dataset provides information
on which governments took action, what action they did, and when they took it. The OxCGRT
systematically gathers information on a range of common policy responses by a given government
and determines the extent to which the government is implementing these measures. The respective
scores are combined into a set of policy indicators.</p>
      <p>The second dataset contains new public data on the geography of COVID-19 cases worldwide
from European Centre for Disease Prevention and Control. Each line or record contains the number of
new cases per day, by country or region.</p>
      <p>For the performed analysis we have merged the mentioned datasets and considered data from
January 01, to October 04.
3.2.</p>
    </sec>
    <sec id="sec-5">
      <title>The Methods Used</title>
      <p>Stochastic gradient enhancement is a solution to a regression problem by building an ensemble of
"weak" predictive decision trees. At the first iteration, a decision tree with a limited number of nodes
is built. The difference between that predicted tree multiplied by the learning rate and the desired
variable at that stage is then calculated. And the next iteration builds on this difference. This continues
until the result stops improving. At every step we try to fix the errors of the previous tree.</p>
    </sec>
    <sec id="sec-6">
      <title>3.2.1. Data Preprocessing</title>
      <p>Dataset consists of attributes with different nature. An approach to processing large, distilled data
was described in [21]. The noise data and outliers are presented in the dataset studied as well. That is
why at the first stage the following steps are required:
• feature selection,
• empty data analysis,
• data normalization and scaling.</p>
      <p>Feature selection is made based on theory of information. The joint mutual information between
each feature and target attribute ConfirmedCases is calculated as:
where c is target class, I(f,c) is mutual information, is already selected feature, is processed
feature.</p>
      <p>The already selected featured were selected manually. The list of the already selected features
looks like the following: countryName, loaddate. As result, 19 from 38 features were selected.</p>
      <p>The next step is empty data analysis. The dataset consists of 66,998 rows, 26,003 of them have
empty values in selected attributes. Due to small quantity of rows with empty data these rows were
eliminated. In addition, binning was made as well.</p>
      <p>
        It is desirable to bring all input variables to a single range and normalize (the maximum absolute
value of input variables should not exceed one). Otherwise, errors due to variables varying over a
wide range will be more influential than errors due to variables varying over a narrow range. By
ensuring that each feature changes within the same range, we ensure that each has an equal effect.
Therefore, the input variables, as a rule, are scaled so that the variables change in the range of the
function, as a rule, [
        <xref ref-type="bibr" rid="ref1">0,1</xref>
        ] or [
        <xref ref-type="bibr" rid="ref1">−1,1</xref>
        ]. The Softmax scaling is used. The distribution of dataset for each
feature is shown in the Figure 1.
      </p>
    </sec>
    <sec id="sec-7">
      <title>4. Results and Findings</title>
      <p>First, the regression decision tree is developed. Decision trees divide an object space according to
a set of splitting rules. These rules are logical statements about a variable and can be true or false.
Three circumstances are key here:
1. the rules make it possible to implement sequential dichotomous data segmentation,
2. two objects are considered similar if they appear in the same segment of the partition,
3. at each step of the partition, the amount of information about the variable under investigation
(response) increases.</p>
      <p>The main feature of the propose algorithm is its  -arc structure. Branching on a chosen trait x
splits training objects on  subsamples, where  is the number of different characteristic values.</p>
      <p>Without loss of generality, we will assume that the feature  has values from {0, 1, …,  -1},  ≥ 2.
In this case, when constructing of the decision tree, from the vertex  there are  arcs labeled with
numbers from {0, 1, …,  -1}. Let  be the label of one of the arcs leaving the vertex  ,  ∈ {0, 1, …,
 -1}. To form a new current subset of objects and a new current set of features, those objects from  ̌
are deleted for which the value of feature  is not equal to  , and also feature  itself is removed from
the set of features.</p>
      <p>Let  be a hanging vertex generated by a branch of a tree with the inner vertices ,…, and let
the arc outgoing from the vertex ,  ∈ {1,…,  }, be labeled   . Further let  ( ) -the current set of
objects that hit the vertex  . The vertex  is associated with a pair ( ,  ( )), where  ( ) is equal to
the mean value of the target variable over all objects from  ( ), and B is an elementary conjunction
of the form … . If the vertex  is not pendant, then we assign to it the conjunction  =  …
... Truth interval of elementary conjunction B denote by 
. Let  be a recognizable object. For
each hanging vertex ( ,  ( )), a check is performed that the description of the test object belongs to
the truth interval  . If the description  belongs to  , then the object  is associated with the value
of the target variable  ( ). Object  is assigned the value of the target variable
where
(a)
(b)
Figure 1: Data distribution before (a) and after (b) preprocessing</p>
      <p>The next step is clustering. The k-means method is used. The gap-statistics allows to find the
appropriative number of clusters.</p>
      <p>Cluster centroids allow to find “average” object in each group and to create the regularization
rules. The cluster # 3 shows countries under restriction, cluster #1 consists of countries without almost
any restriction (see Table 1, Table 2, Table 3).
2.</p>
      <p>15000
t10000
n
u
o
c
5000
0
12000
9000
tun6000
o
c
3000
0</p>
      <p>As it can be seen from the Figure 2 the clusters differ by the most distinct recommendations,
which can be summarized as follows:
• Cluster #1: recommended to close schools, and control international travels,
• Cluster #2: recommended to stay at home,
• Cluster #3: recommended to stay at home and cancel public events.</p>
      <p>The influence of such clustering on COVID-19 spreading, peak position and duration as well as
mortality rate will be the subject of our further study.</p>
      <p>An example of countries along with the most frequent cluster number is given in Table 4. The
same country can be joined to different clusters in different time slots. So, the clustering by country
will not be so unambiguous. That is why time series for separated country can be interesting and will
be the subject of the further study. At this stage we used the classification routine on the dataset. The
comparison of rule-based, statistical and recurrent neural network methods can also be found at [22].</p>
      <p>Three classifiers are analyzed: random forest (500 trees), logistic regression and XGBOOST (tree
learning algorithm). The scores of the models are listed in Table 5.</p>
      <p>The rules given below presents the strategy based on decision tree and can be used for strategic
planning in the public health system to avoid deaths and severe consequences of the epidemic.
if ( confirmedcases &lt;= 11577.5 ) {
if ( confirmedcases &lt;= 3806.5 ) { [[confirmeddeaths=20.21931171]] }</p>
      <p>else { [[ confirmeddeaths =206.84760845]] }
} else {
if ( confirmedcases &lt;= 17153.5 ) {
if ( e1_income_support &lt;= 1.5 ) {
else {
if ( c8_international_travel_controls &lt;= 2.5 ) {
if ( c6_stay_at_home_requirements &lt;= 0.5 ) { [[confirmeddeaths=452.20754717]] }
else { [[confirmeddeaths=1410.8028169]] }
} else { [[confirmeddeaths=501.40616622]] }</p>
    </sec>
    <sec id="sec-8">
      <title>5. Conclusions and Future Work</title>
      <p>The current COVID-19 pandemic poses serious challenges for data scientists and AI professionals
due to limited and incomplete data and the large amount of heterogeneous data, as well as the
significant impact of various factors on disease behavior and spread.</p>
      <p>This paper is devoted to building the recommendation rules for appropriated state policy for
reducing the spread of new Covid-19 cases. The system of these rules is based on novel ensemble of
machine learning methods such as regression tree and clustering. The merged data from the Oxford
COVID-19 Government Response Tracker and ECDC Covid-19 Cases datasets were used in this
study.
[[confirmeddeaths=1346.375]]</p>
      <p>The clustering was carried out using the k-means method. The gap-statistics allows to find the
appropriative number of clusters, and in the case of the study three clusters were selected. The clusters
differ by the recommendations and actions made by the correspondent governments. Thus the first
cluster countries chose to close schools and to control international travels as main recommendations;
the second cluster countries recommended to stay at home, while the major recommendations of
governments of countries belonging to the third cluster were to stay at home and to cancel public
events.</p>
      <p>The same country can be joined to different clusters in different time slots. So, the clustering by
country will not be so unambiguous. That is why time series for separated country can be interesting
and will be the subject of the further study. Besides, the influence of such clustering on COVID-19
spreading, peak position and duration as well as mortality rate will also be the subject of our further
study.</p>
      <p>The regression decision tree was built, and the set of rules was extracted from the decision tree and
can be used for strategic planning in the public health system.</p>
      <p>We believe that the results obtained in this article will contribute to the public good for solving the
current global problem. It is also seen that it is necessary to reduce the infection rate sharply and
quickly to see a noticeable decrease in the epidemic peak and the death rate.
6. References
[13] Basu, S., Campbell, R.H. Going by the numbers : Learning and modeling COVID-19 disease
dynamics. Chaos, Solitons &amp; Fractals 138 (2020), 110140.
https://doi.org/10.1016/j.chaos.2020.110140
[14] R.A. Neher, R. Dyrdak, V. Druelle, E.B. Hodcroft, J. Albert. Potential impact of seasonal forcing
on a SARS-CoV-2 pandemic. Swiss Med Weekly, 150 (1112) (2020).
https://doi.org/10.4414/smw.2020.20224
[15] COVID-19 Scenarios. URL: https://neherlab.org/covid19/
[16] Hu Z, Ge Q, Jin L, Xiong M. Artificial intelligence forecasting of COVID-19 in China. arXiv
preprint arXiv:200207112 2020. http://arxiv.org/abs/200207112
[17] Bandyopadhyay SK, Dutta S. Machine learning approach for confirmation of COVID-19 cases:
positive, negative, death and release. medRxiv 2020.
https://doi.org/10.1101/2020.03.25.20043505
[18] Z. Yang, Z. Zeng, K. Wang, S.-S. Wong, W. Liang, M. Zanin, et al. Modified SEIR and AI
prediction of the epidemics trend of COVID-19 in China under public health interventions. J
Thorac Dis, 12 (3) (2020), p. 165. https://doi.org/10.21037/jtd.2020.02.64
[19] S. Tuli, S. Tuli, R. Tuli, S.S. Gill. Predicting the growth and trend of COVID-19 pandemic using
machine learning and cloud computing. Internet of Things 11 (2020), 100222.
https://doi.org/10.1016/j.iot.2020.100222
[20] COVID-19 Data Lake. URL:
https://azure.microsoft.com/en-US/services/opendatasets/catalog/covid-19-data-lake/
[21] Boyko, N., Mochurad, L., Stetsiv, I., Kryvenchuk, Yu.: Modeling of the Information System for
Processing of a Large Distilled Data for the Investigation of Competitiveness of Enterprises. In:
Proc. of the 4th Intl Conf. on Computational Linguistics and Intelligent Systems (COLINS
2020). Volume I: Main Conference Lviv, Ukraine, April 23–24, 2020, pp. 964–978.
CEURWS.org, online CEUR-WS.org/Vol-2604/paper64.pdf
[22] Boyko, N., Mochurad, L., Parpan, U., Basystiuk, O.: Usage of Machine-based Translation
Methods for Analyzing Open Data in Legal Cases. In: Proc. of the Intl Workshop on Cyber
Hygiene (CybHyg-2019) co-located with 1st International Conference on Cyber Hygiene and
Conflict Management in Global Information Networks (CyberConf 2019), Kyiv, Ukraine,
November 30, 2019, pp. 328–338. CEUR-WS.org, online CEUR-WS.org/Vol-2654/paper26.pdf</p>
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  </body>
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