Calculation of index and singular points of linear differential-algebraic equations of higher order. Neliniini Kolyvannya, [S. l.], v. 20, n. 2, p. 274–288, 2017. Disponível em: https://twinhead.imath.kiev.ua/index.php/nosc/article/view/868. Acesso em: 21 jan. 2026.