Rozhko, Mikhail Viktorovich, Vladimir Anatolyevich Rubtzov, y Niyaz Kamilevich Gabdrakhmanov. 2017. «Positioning of the Republic of Mari El in Volga Federal District». Revista Publicando 4 (13 (3). "Quito, Ecuador":905-15. https://revistapublicando.org/revista/index.php/crv/article/view/1015.