ŠPACAPAN, Simon, 2011, The k-independence number of direct products of graphs and Hedetniemi’s conjecture. European journal of combinatorics [na spletu]. 2011. Vol. 32, no. 8, p. 1377–1383. [Dostopano 22 januar 2025]. Pridobljeno s: http://dx.doi.org/10.1016/j.ejc.2011.07.002