theorem Th180:
  for G1 being addVertices of G2, V
  holds G1 is finite-tcolorable iff G2 is finite-tcolorable
proof
  let G1 be addVertices of G2, V;
  hereby
    assume A1: G1 is finite-tcolorable;
    G2 is Subgraph of G1 by GLIB_006:57;
    hence G2 is finite-tcolorable by A1;
  end;
  assume G2 is finite-tcolorable;
  then consider n such that
    A2: G2 is n-tcolorable;
  G1 is n-tcolorable by A2, Th169;
  hence thesis;
end;
