1. R. Bacher, (mathoverflow.net/users/4556), “Antipodal” maps on regular graphs? http://mathoverflow.net/questions/64804 (version: 2011-05-15).
2. Geodesics in non-positively curved plane tessellations;Baues;Adv. Geom.,2006
3. Curvature and geometry of tessellating plane graphs;Baues;Discrete Comput. Geom.,2001
4. A Panoramic View of Riemannian Geometry;Berger,2002
5. J. Boland, M. Miller, The eccentric digraph of a digraph. In: Proc. 12th Australasian Workshop Combin. Algorithms (AWOCA 2001) 66–70.