reserve U0 for Universal_Algebra,
  U1 for SubAlgebra of U0,
  o for operation of U0;

theorem Th3:
  for U1 be SubAlgebra of U0 holds the carrier of U1 c= the carrier of U0
proof
  let U1 be SubAlgebra of U0;
  the carrier of U1 is Subset of U0 by UNIALG_2:def 7;
  hence thesis;
end;
