let G1 be _Graph; :: thesis: for G2, G3 being DLGraphComplement of G1 holds G3 is G2 -Disomorphic
let G2, G3 be DLGraphComplement of G1; :: thesis: G3 is G2 -Disomorphic
G1 is G1 -Disomorphic by GLIB_010:53;
hence G3 is G2 -Disomorphic by Th49; :: thesis: verum