KOROBEINIK, J. F. On integral solutions of the differential equation of infinite order with polynomial coefficients. Lithuanian Mathematical Journal, [S. l.], v. 4, n. 2, p. 203–227, 1964. DOI: 10.15388/LMJ.1964.19500. Disponível em: https://www.journals.vu.lt/LMJ/article/view/19500. Acesso em: 14 apr. 2025.