PRYKARPATSKY, Ya. A.; SAMOILENKO, A. M. The classical M. A. Buhl problem, its Pfeiffer – Sato solutions and the classical Lagrange – D’Alembert principle for the integrable heavenly type nonlinear equations. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 69, n. 12, p. 1652–1689, 2017. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/1811. Acesso em: 5 dec. 2025.