“The Exterior Tricomi and Frankl Problems for Quaterelliptic-Quaterhyperbolic Equations With Eight Parabolic Lines”. European Journal of Pure and Applied Mathematics 4, no. 2 (May 17, 2011): 186–208. Accessed November 21, 2024. https://www.ejpam.com/index.php/ejpam/article/view/1175.