Ilieva, Margarita, and Iliya Iliev. “Bulgarian Urban Settlements in the Early 21st Century”. Bulletin of Geography. Socio-economic Series, no. 13 (July 5, 2010): 113–126. Accessed April 23, 2024. https://apcz.umk.pl/BGSS/article/view/v10089-010-0009-y.