1. Ashrafi N., Maimani H.R., Pournaki M.R., Yassemi S: Unit graphs associated with rings. Commun. Algebra 38, 2851–2871 (2010)
2. Bondy, J.A.; Murty, U.S.R.: Graph Theory with Applications. American Elsevier Publishing Co., Inc., New York (1976)
3. Ehrlich G: Unit-regular rings. Portugal. Math. 27, 209–212 (1968)
4. Goldsmith, B.; Pabst, S.; Scott, A.: Unit sum numbers of rings and modules. Q. J. Math. Oxford Ser. (2) 49(195), 331–344 (1998)
5. Grimaldi, R.P.: Graphs from rings. Proceedings of the twentieth southeastern conference on combinatorics, graph theory, and computing (Boca Raton, FL, 1989), Congr. Numer. 71, 95–103 (1990)