CELLINA, Arrigo. Some problems in the Calculus of Variations. Annales Mathematicae Silesianae, [S. l.], v. 31, p. 5–55, 2017. Disponível em: https://journals.us.edu.pl/index.php/AMSIL/article/view/13937. Acesso em: 15 dec. 2025.