PrykarpatskyYa. A., and SamoilenkoA. 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 69, no. 12 (December 25, 2017): 1652-1689. Accessed November 23, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/1811.