MAHER, A.; UTKKINA, Y. A. The variant of the Goursat problem for the sixth order equation. Tamkang Journal of Mathematics, [S. l.], v. 37, n. 4, p. 309-316, 2006. DOI: 10.5556/j.tkjm.37.2006.145. Disponível em: https://journals.math.tku.edu.tw/index.php/TKJM/article/view/145. Acesso em: 25 jul. 2021.