Gubaidullin , Airat M. “On Some Issues of Studying the Pre-Mongol Bolgar Fortified Settlements”. Arkheologiia Evraziiskikh Stepei (Archaeology of the Eurasian Steppes), no. 3 (June 30, 2026): 226–232. Accessed November 7, 2026. https://www.evrazstep.ru/index.php/aes/article/view/1913.