SKRZYPCZYK, Jerzy. Perturbation Methods for Acoustic Systems with Interval Parameters. Archives of Acoustics, [S. l.], v. 33, n. 4(S), p. 165–170, 2008. Disponível em: https://acoustics3.ippt.pan.pl/index.php/aa/article/view/853. Acesso em: 26 apr. 2025.