LEBID, V. O.; NIZHNIK, L. P. Spectral analysis of locally finite graphs with one infinite ray . Reports of the National Academy of Sciences of Ukraine, Kyiv, Ukraine, n. 3, p. 29–35, 2014. DOI: 10.15407/dopovidi2014.03.029. Disponível em: https://nasu-periodicals.org.ua/index.php/dp/article/view/15604. Acesso em: 20 jun. 2026.