CELLINA, Arrigo. Some problems in the Calculus of Variations. Annales Mathematicae Silesianae, [S. l.], v. 31, p. 5–55, 2017. Disponível em: https://trrest.vot.pl/ojsus/index.php/AMSIL/article/view/13937. Acesso em: 7 may. 2025.