DUDLEY, R. M. On second derivates of convex functions. MATHEMATICA SCANDINAVICA, [S. l.], v. 41, p. 159–174, 1977. DOI: 10.7146/math.scand.a-11710. Disponível em: https://www.mscand.dk/article/view/11710. Acesso em: 5 may. 2024.