
theorem
  for S,T being feasible ManySortedSign st the carrier of T c= the
  carrier of S & the Arity of T = (the Arity of S)|the carrier' of T & the
  ResultSort of T = (the ResultSort of S)|the carrier' of T holds T is
  Subsignature of S
proof
  let S,T be feasible ManySortedSign such that
A1: the carrier of T c= the carrier of S;
  assume that
A2: the Arity of T = (the Arity of S)|the carrier' of T and
A3: the ResultSort of T = (the ResultSort of S)|the carrier' of T;
  the Arity of T c= the Arity of S by A2,RELAT_1:59;
  hence thesis by A1,A3,Th13,RELAT_1:59;
end;
