let G1 be _Graph; :: thesis: for G2, G3 being DGraphComplement of G1 holds G3 is G2 -Disomorphic
let G2, G3 be DGraphComplement of G1; :: thesis: G3 is G2 -Disomorphic
G1 is G1 -Disomorphic by GLIB_010:53;
hence G3 is G2 -Disomorphic by Th84; :: thesis: verum