FREILING, G.; YURKO, V. Recovering Sturm-Liouville operators on hedgehog-type graphs with general matching conditions. Eurasian Mathematical Journal, [S. l.], v. 5, n. 4, p. 56–69, 2014. Disponível em: https://emj.enu.kz/index.php/main/article/view/588. Acesso em: 18 sep. 2025.