KARLOVA, O. O.; MYKHAILYUK, V. V. Upper and lower Lebesgue classes of multivalued functions of two variables. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 70, n. 8, p. 1097–1106, 2018. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/1620. Acesso em: 17 apr. 2025.