“…The second equally important motivation is the Infinite Motion Conjecture of Tucker [28], who conjectured that each connected, locally finite infinite graph is 2-distinguishable, if every automorphism that is not the identity moves infinitely many vertices. The conjecture is still open, although it has been shown to be true for many classes of graphs [9,17,27], in particular for graphs of subexponential growth [22], and thus for all graphs of polynomial growth. For a long time it was not clear whether it holds for graphs of maximal valence 3, and whether infinite motion was really needed.…”