DANICKI, E. Spectral theory of natural unidirectionality of SPUDT for BG waves. Archives of Acoustics, [S. l.], v. 16, n. 1, p. 73–78, 2014. Disponível em: https://acoustics.ippt.gov.pl/index.php/aa/article/view/1211. Acesso em: 17 jan. 2026.