ZHURAEV, D. A. Cauchy problem for matrix factorizations of the Helmholtz equation. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 69, n. 10, p. 1364–1371, 2017. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/1787. Acesso em: 6 dec. 2025.