The Exterior Tricomi and Frankl Problems for Quaterelliptic-Quaterhyperbolic Equations with Eight Parabolic Lines. Eur. J. Pure Appl. Math. [Internet]. 2011 May 17 [cited 2025 Apr. 1];4(2):186-208. Available from: https://www.ejpam.com/index.php/ejpam/article/view/1175