Taystruk, O. and Pivovarchik, V.N. (2014) “Spectral problem for a graph of symmetric Stieltjes strings”, Methods of Functional Analysis and Topology, 20(2), pp. 164–174. Available at: https://zen.imath.kiev.ua/index.php/mfat/article/view/576 (Accessed: 15 December 2025).