T. Kaloyanov, “Extramarital Birth-Rate in the Republic Of Bulgaria – Trends and Territorial Differences during the 1995-2015 Period”, НТ, no. 1, pp. 11–33, Jul. 2017, Accessed: Jul. 23, 2026. Available: https://bjiep.e-dnrs.org/index.php/rp/article/view/5622