HUMMEL, J. A.; SCHIFFER, M. M. Variational methods for Bieberbach-Eilenberg functions and for pairs. Annales Fennici Mathematici, [S. l.], v. 2, n. 1, p. 3–42, 1976. DOI: 10.5186/aasfm.1977.0310. Disponível em: https://afm.journal.fi/article/view/134269. Acesso em: 25 nov. 2024.