Kabytov, Petr, Edward Dubman, and Olga Leontieva. “The Middle Volga and Trans-Volga Region in the Context of Development of the Russian State System: A Modern Concept”. Quaestio Rossica, no. 2 (1): 117 -. Accessed July 25, 2021. https://qr.urfu.ru/ojs/index.php/qr/article/view/099.