## 2 Materials and Methods  
The initial step was to investigate the existing literature in order to identify the most suitable database for the bibliometric analysis. ISI Web of Science, known also as ClarivateAnalytics' Web of Science Core Collection or WoS [21], was chosen as the database used for the papers' extraction [22; 23; 24; 25; 26]. [PERSON] et al. [27] explained why WoS is the best database to perform a bibliometric analysis, having a variety of journals and domains, most of them recognized and known in the academic community. Even if the level of inclusivity is smaller compared with other databases, the WoS database is still one of the best sources for researchers. Also, the choice of this database has been further highlighted by [PERSON] [28]. The author mentions the number of publications included, their subject distribution, and their geographical distribution among the reasons for choosing this database. The majority of ISI Web of Science documents are published in English and have a wider journal coverage compared to Dimensions, IEEE, or Scopus databases, with a total of 74.8 million scholarly datasets and over 1.5 billion cited references, describing a diversity of academic topics [29]. [PERSON] et al. [29] explained that WoS coverage improved significantly starting in 1990, indexing over 13,610 journals and 13 million publications as of June 2020. Even if the Scopus database has more papers (18 million as of June 2020), the impact of Scopus-indexed journals is smaller compared to those indexed by WoS. Furthermore, it should be stated that the WoS database offers, within the extracted dataset, a special feature related to the papers included in the dataset, called Keywords Plus [30]. This special class of keywords is extracted based on the references in the papers included in the dataset, helping in better shaping the information included in the studies. A detailed analysis of the existing research has been carried out, in order to understand how to extract documents from Clarivate Analytics' Web of Science Core Collection. [PERSON] [31; 32] explained the main steps that should be taken in the extraction process. A crucial point that should be mentioned is that the WoS database is subscription-based, meaning that the results can be differentiated based on the subscription type. At the same time, some of the subscriptions offer limited access to specific indexes, while other subscriptions provide access to a variety of indexes and papers, and, as [PERSON] [32] highlighted, it is crucial for authors to investigate and explain the indexes that are available with their subscription. The subscription influences the total number of papers that are extracted from WoS, and in our case, the indexes that were available are detailed below:  
* Social Sciences Citation Index (SSCI)--1975-present;
* Book Citation Index--Science (BKCI-S)--2010-present;
* Emerging Sources Citations Index (ESCI)--2005-present;
* Science Citation Index Expanded (SCIE)--1900-present;
* Index Chemicus (IC)--2010-present;
* Book Citation Index--Social Sciences and Humanities (BKCI-SSH)--2010-present;
* Arts and Humanities Citation Index (A&HCI)--1975-present;
* Conference Proceedings Citation Index--Science (CPCI-S)--1990-present;
* Conference Proceedings Citation Index--Social Sciences and Humanities (CPCI-SSH)--1990-present;
* Current Chemical Reactions (CCR-Expanded)--2010-present;  
In Figure 1 are detailed the main steps that should be performed for a bibliometric analysis, according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses, also known as the PRISMA flowchart. [PERSON] et al. [33] explained that PRISMA comprises a set of rules and recommendations used mainly for transparent and complete reporting of systematic reviews, offering the possibility to develop appropriate analyses of papers and include all aspects accurately. The first step consists of dataset Identification, where the documents are related to time series forecasting and artificial intelligence.