 This construction justifies one of the alternative names of the Laves graph, the "K"4 crystal.One way to construct a maximal abelian covering graph from a smaller graph "G" (in this case "K"4) is to choose a spanning tree of "G", let "d" be the number of edges that are not in the spanning tree (in this case, three non-tree edges), and to choose a distinct unit vector in formula_4 for each of these non-tree edges.Then, fix the set of vertices of the covering graph to be the ordered pairs ("v","w") where "v" is a vertex of "G" and "w" is a vector in formula_4.