GUNDERSEN, G.; STEINBART, E. M.; WANG, S. Solutions of nonhomogeneous linear differential equations with exceptionally few zeros. Annales Fennici Mathematici, [S. l.], v. 23, n. 2, p. 429–452, 1998. Disponível em: https://afm.journal.fi/article/view/134927. Acesso em: 25 nov. 2024.