KLAVŽAR, Sandi, 2002, Brešar, Boštjan: On the natural imprint function of a graph. - European J. Combin. 23 (2002), no. 2, 149-161. Mathematical reviews [na spletu]. 2002. Vol. 2002k. [Dostopano 31 marec 2025]. Pridobljeno s: http://www.ams.org/mathscinet/pdf/1881547.pdf