DUDKO, A.; PIVOVARCHIK, V. N. Three spectra problems for star graph of Stieltjes strings. Methods of Functional Analysis and Topology, [S. l.], v. 25, n. 4, p. 311–323, 2019. Disponível em: https://zen.imath.kiev.ua/index.php/mfat/article/view/735. Acesso em: 15 dec. 2025.