About solvabiblity of a class of optimal control problems controlling the coefficients of the principal part of a nonlinear ellyptic operator. Neliniini Kolyvannya, [S. l.], v. 12, n. 1, p. 59–72, 2009. Disponível em: https://twinhead.imath.kiev.ua/index.php/nosc/article/view/507. Acesso em: 21 jan. 2026.