Ruy Fabila Monroy David Flores-Peñaloza Clemens Huemer Ferran Hurtado Jorge Urrutia David R. Wood Token Graphs. 365-380 2012 28 Graphs and Combinatorics 3 http://dx.doi.org/10.1007/s00373-011-1055-9 db/journals/gc/gc28.html#MonroyFHHUW12