**2. Contributions**

After careful evaluation, seventeen papers were accepted and are published in the Special Issue.

The Special Issue raised the interest of researchers from different scientific schools in Europa, Asia and South America. Sixty-seven researchers from sixteen different countries contributed to the published papers (Figure 1). The most significant number of researchers were from Lithuania. Ten authors contributed from Serbia and China. From the other remaining countries, one to four authors participated.

**Figure 1.** The number of authors from different countries.

Publications were evenly distributed according to whether authors produced them from one country or by international collectives: authors prepared nine papers from one country and the other eight were from international collectives (Table 1). Leading countries by the number of publications are Lithuania (three national collectives and four international collectives) and the Czech Republic (two papers).



The authors proposed different solution models, mainly covering uncertain data in multi-criteria decision-making problems, as complex tools to deal with complicated problems in engineering or management (Table 2).


**Table 2.** Publications by solution methods and application areas.

More than half of the papers proposed different, multiple-criteria decision-making models, mainly dealing with uncertain data. Fuzzy sets [54,57,67] or single-valued neutrosophic sets [55,61,65,66] were the most often applied for modelling uncertain data.

The application fields of the proposed solution models rather often involved different engineering problems. Much attention was given to civil engineering in terms of construction project management [56,58] and the analysis of building structures [59,61]. Three papers analysed the optimisation of supply chains [62,64,66]. Two papers aimed to optimise e-activities, namely, to rank e-commerce development strategies [65] and to evaluate e-learning courses [67]. Two papers solved mechanical medical problems in rehabilitation [60,63]. An up-to-date medical-area problem was solved in [68], namely, location selection of a temporary hospital during the COVID-19 pandemic. It is worth mentioning the excellent article published in the current Special Issue, which is the bibliometric analysis of publications in the *Symmetry* journal from 2009 to 2019 [23], which helps readers to

understand past and current research scopes of the journal as well as future trends of its development.
