theorem Th74:
  U-Veblen.1 = criticals(U exp omega)
  proof set o = succ(0-element_of U);
    o in On U by ORDINAL1:def 9; then
    U-Veblen.1 = criticals(U-Veblen.0) by Def15;
    hence thesis by Def15;
  end;
