GUNDERSEN, G. G. On the real zeros of solutions of f’’ + A(z)f = 0 where A(z) is entire. Annales Fennici Mathematici, [S. l.], v. 11, n. 2, p. 275–294, 1986. DOI: 10.5186/aasfm.1986.1105. Disponível em: https://afm.journal.fi/article/view/134576. Acesso em: 25 nov. 2024.