K13 challenge
nauty code (nauty.h naututil.h rng.h nauty.c naututil.c rng.c nautil.c naugraph.c) (c) Brendan McKay and Adolfo Piperno
http://cs.anu.edu.au/~bdm/nauty/
K11 code (#0_K4.txt dgraph.h main.cpp readme.pdf) (c) Sengjun Pan and R. Bruce Richter