Aleksander Malnic Dragan Marusic Rögnvaldur G. Möller Norbert Seifter Vladimir Ivanovich Trofimov Boris Zgrablic Highly arc transitive digraphs: reachability, topological groups. 19-28 2005 26 Eur. J. Comb. 1 http://dx.doi.org/10.1016/j.ejc.2004.02.006 db/journals/ejc/ejc26.html#MalniMMSTZ05