TLEUBERGENOV, M.I.; AZHYMBAEV, D.T. Stochastical problem of Helmholtz for Birkhoff systems. Bulletin of the Karaganda University. Mathematics Series, [S. l.], v. 93, n. 1, p. 78–87, 2019. DOI: 10.31489/2019m1/78-87. Disponível em: http://mts.buketov.edu.kz/index.php/mathematics-vestnik/article/view/279. Acesso em: 7 sep. 2025.