KLAVŽAR, Sandi, 2005, Bendall, Sarah; Hammack, Richard: Centers of $n$-fold tensor products of graphs. (English summary). - Discuss. Math. Graph Theory 24 (2004), no. 3, 491--501. [online]. 2005. [Accessed 3 April 2025]. Retrieved from: http://www.ams.org/mathscinet/pdf/2120072.pdf