
theorem Th105:
  for G1, G2, G3 being _Graph, F1 being PGraphMapping of G1, G2,
    F2 being PGraphMapping of G2, G3
  st F2 is onto & dom F2_V c= rng F1_V & dom F2_E c= rng F1_E
  holds F2 * F1 is onto by RELAT_1:28;
