reserve U1,U2,U3 for Universal_Algebra,
  m,n for Nat,
  a for set,
  A for non empty set,
  h for Function of U1,U2;

theorem
  h is_isomorphism implies MSAlg h is_isomorphism MSAlg U1,(MSAlg
  U2 Over MSSign U1)
by Th18,Th19;
