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

theorem
  for U0 being with_const_op Universal_Algebra for U1 being strict
  SubAlgebra of U0 holds Constants(U0) c= (Carr U0).U1
proof
  let U0 be with_const_op Universal_Algebra;
  let U1 be strict SubAlgebra of U0;
  U1 in Sub(U0) by Th1;
  then
A1: (Carr U0).U1 = the carrier of U1 by Def4;
  Constants(U1) = Constants(U0) by Th6;
  hence thesis by A1;
end;
