
theorem Th22:
  for G1, G2 being _Graph, F being directed PGraphMapping of G1, G2
  st F_V is one-to-one & rng F_E = the_Edges_of G2 holds F is Dcontinuous
proof
  let G1, G2 be _Graph, F be directed PGraphMapping of G1, G2;
  assume A1: F_V is one-to-one & rng F_E = the_Edges_of G2;
  then F is semi-Dcontinuous by Th18;
  hence thesis by A1, Th20;
end;
