SHIN, K. New polynomials P for which f’’+P(z)f=0 has a solution with almost all real zeros. Annales Fennici Mathematici, [S. l.], v. 27, n. 2, p. 491–498, 2002. Disponível em: https://afm.journal.fi/article/view/135058. Acesso em: 11 apr. 2025.