1. Polynomial invariants of graphs on surfaces;Askanazi;Quantum Topol.,2013
2. A polynomial for graphs on orientable surfaces;Bollobás;Proc. Lond. Math. Soc.,2001
3. A polynomial of graphs on surfaces;Bollobás;Math. Ann.,2002
4. C. Butler, A quasi-tree expansion of the Krushkal polynomial. Preprint arXiv:1205.0298.
5. C. Chun, I. Moffatt, S. Noble, R. Rueckriemen, Matroids, delta-matroids and embedded graphs. Preprint, arXiv:1403.0920.