LONKA, H.; TAMMI, O. On the use of step-functions in extremum problems of the class with bounded boundary rotation. Annales Fennici Mathematici, [S. l.], n. 418, 1968. DOI: 10.5186/aasfm.1968.418. Disponível em: https://afm.journal.fi/article/view/134094. Acesso em: 26 nov. 2024.