1. 1. Andreeva P., Andreev A. (2020), On the problems related to the implementation of geographic information systems in Bulgaria. [online], URL: https://www.aadcf.nvu.bg/scientific_events/papers/dtf2020.pdf. Accessed on 28.11.2021
2. 2. Antipova E., Fakeyeva L. (2012), Settlement system of Belarus: spatial and temporal trends at the end of 20th and the beginning of the 21st centuries. Journal of Settlements and Spatial Planning, 3 (2), 129–139. URL: http://geografie.ubbcluj.ro/ccau/jssp/arhiva_2_2012/09JSSP022012.pdf
3. 3. Delgado Viñas C. (2013), Population Dynamics of Spanish Mountain Areas: Case Study of Two Regions in the Cantabrian Mountains (Spain). Journal of Settlements and Spatial Planning, Special Issue (2), 207-217. URL: https://geografie.ubbcluj.ro/ccau/jssp/arhiva_si2_2013/04JSSPSI022013.pdf
4. 4. ESRI (2014), An overview of the Mapping Clusters toolset. [online], URL: https://desktop.arcgis.com/en/arcmap/10.3/tools/spatial-statistics-toolbox/an-overview-of-the-mapping-clusters-toolset.htm. Accessed on 05.06.2021
5. 5. ESRI (2014), How Grouping Analysis works. [online], URL: https://desktop.arcgis.com/en/arcmap/10.3/tools/spatial-statistics-toolbox/grouping-analysis.htm. Accessed on 05.06.2021