TASMAMBETOV , Zh. N. One system of differential equations in partial derivatives of the second order. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 44, n. 3, p. 427–430, 1992. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/8113. Acesso em: 14 apr. 2025.