1. Albeverio S., Gesztesy F., Høegh-Krohn R., Holden H.: Solvable Models in Quantum Mechanics, 2nd ed., With an Appendix by Pavel Exner. AMS Chelsea publishing, Rhode Island (2005)
2. Bardhan, G., Kuchment P.: Introduction to Quantum Graphs. AMS Providence, RL (2012)
3. Carlson R.: Hill’s equation for a homogeneous tree. Electron. J. Differ. Equ. 23, 1–30 (1997)
4. Cheon T., Exner P., Turek O.: Spectral filtering in quantum Y-junction. J. Phys. Soc. Jpn. 78, 124004 (2009)
5. Do N.T., Kuchment P.: Quantum graph spectra of a graphyne structure. Nanoscale Syst. 2, 107–123 (2013)