ZORIY , N. V. On variational problems of the theory of potential. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 43, n. 3, p. 347–354, 1991. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/9614. Acesso em: 6 dec. 2025.