KLAVŽAR, Sandi, 2005, Gutman, Ivan(YU-KRASC); Furtula, Boris(YU-KRASC); Toropov, Andrey A.; Toropova, Alla P.: The graph of atomic orbitals and its basic properties. II. Zagreb indices. (English summary). - MATCH Commun. Math. Comput. Chem. 53 (2005), no. 1, 225--230. [na spletu]. 2005. [Dostopano 8 januar 2025]. Pridobljeno s: http://www.ams.org/mathscinet/pdf/2135472.pdf