Boyko, O.P. et al. 2021. On the second largest multiplicity of eigenvalues for the Stieltjes string spectral problem on trees. Methods of Functional Analysis and Topology. 27, 3 (Sep. 2021), 217–226. DOI:https://doi.org/https://doi.org/10.31392/MFAT-npu26_3.2021.03.