1. D. Bokal, G. Fijavž, B. Mohar, The minor crossing number, manuscript, 2005
2. The Robertson–Seymour theorems: A survey of applications;Fellows,1989
3. Computers and Intractability;Garey,1979
4. Crossing number is NP-complete;Garey;SIAM J. Algebraic Discrete Methods,1983
5. I. Gitler, J. Leanos, G. Salazar, Crossing numbers of projective graphs, manuscript, 2005