TELEGA, J.J. Extremum principles for nonpotential and initial-value problems. Archives of Mechanics, Warsaw, Poland, v. 54, n. 5-6, p. 663–690, 2002. Disponível em: https://am.ippt.pan.pl/index.php/am/article/view/v54p663. Acesso em: 19 nov. 2025.