GILBERT, R. P.; KUKRAL, D. K. A Function-Theoretic Method for &#916;<sub>3</sub> + F(x<sub>1</sub>, x<sub>2</sub>)u = 0*. The Journal of the Indian Mathematical Society, [S. l.], v. 38, n. 1-4, p. 227–231, 1974. Disponível em: http://www.informaticsjournals.com/index.php/jims/article/view/16696. Acesso em: 29 apr. 2024.