take the empty one-to-one continuous PVertexMapping of G1,G2 ; :: thesis: ( the empty one-to-one continuous PVertexMapping of G1,G2 is empty & the empty one-to-one continuous PVertexMapping of G1,G2 is invertible )
thus ( the empty one-to-one continuous PVertexMapping of G1,G2 is empty & the empty one-to-one continuous PVertexMapping of G1,G2 is invertible ) ; :: thesis: verum