For every homomorphism φ of a graph G there exists a contraction θ_φ on G, the complement of G. Here we study the graph equation φ(G)=θ_φ(G). In the course of our work we show that Hadwiger's Conjecture is true for every self-complementary graph.
GILLMAN, R. A. (1995). HOMOMORPHISM AND SIGMA POLYNOMIALS. International Journal of Mathematics and Mathematical Sciences, 1995(), 653-658. https://doi.org/10.1155/S0161171295000834