Exact solutions of a nonlinear wave equation $u_{00}-\bigtriangledown \[u\bigtriangledown u]=0$. Neliniini Kolyvannya, [S. l.], v. 2, n. 3, p. 426–432, 1999. Disponível em: https://twinhead.imath.kiev.ua/index.php/nosc/article/view/77. Acesso em: 22 jan. 2026.