We give a detailed algebraic characterization of when a graph G can be imbedded in the projective plane. The characterization is in terms of the existence of a dual graph G∗ on the same edge set as G which satisfies algebraic conditions inspired by homology groups and intersection products in homology groups.
& Slilaty, D.
(2003). An Algebraic Characterization of Projective-Planar Graphs. Journal of Graph Theory, 42, 320-331.