reserve S for non void non empty ManySortedSign,
  U1 for MSAlgebra over S,
  o for OperSymbol of S,
  s for SortSymbol of S;

theorem
  for U1,U2 be non-empty MSAlgebra over S, F be ManySortedFunction of U1
  ,U2 st F is_epimorphism U1,U2 holds QuotMSAlg (U1,MSCng F),U2 are_isomorphic
proof
  let U1,U2 be non-empty MSAlgebra over S, F be ManySortedFunction of U1,U2;
  assume F is_epimorphism U1,U2;
  then MSHomQuot(F) is_isomorphism QuotMSAlg (U1,MSCng F),U2 by Th5;
  hence thesis;
end;
