
theorem Th103:
  for G1, G2, G3 being _Graph, F1 being PGraphMapping of G1, G2,
    F2 being PGraphMapping of G2, G3
  st F1 is total & rng F1_V c= dom F2_V & rng F1_E c= dom F2_E
  holds F2 * F1 is total by RELAT_1:27;
