O. Taystruk and V. N. Pivovarchik, “Spectral problem for a graph of symmetric Stieltjes strings”, MFAT, vol. 20, no. 2, pp. 164–174, Jun. 2014, Accessed: Feb. 04, 2026. [Online]. Available: https://zen.imath.kiev.ua/index.php/mfat/article/view/576