“…Independently of these investigations, many people considered the graph G(R, R * ) in the case when R is a finite ring or an Artinian ring. Various properties of these graphs, including connectivity, diameters and chromatic numbers, were studied among others in the papers by Dejter and Giudici [5], Berrizbeitia and Giudici [4], Fuchs [12], Klotz and Sander [31], Lucchini and Maróti [35], Lanski and Maróti [32], Akhtar, Boggess, Jackson-Henderson, Jiménez, Karpman, Kinzel and Pritkin [2] and Khashyarmanesh and Khorsandi [30]. In these works the graph G(R, R * ) is usually called unitary Cayley graph.…”