English: The Clebsch graph, labeled for the reduction of Keller's cube-tiling conjecture to a graph clique problem by Corrádi and Szabó. This graph represents the two-dimensional case of the conjecture, and the truth of the conjecture for this case follows from the fact that it has no four-vertex clique (more strongly it has no triangle). However, the graphs resulting from higher dimensional versions of the conjecture have large cliques, from which it follows that the conjecture it is false.