reserve i for Nat,
  j for Element of NAT,
  X,Y,x,y,z for set;
reserve C for initialized ConstructorSignature,
  s for SortSymbol of C,
  o for OperSymbol of C,
  c for constructor OperSymbol of C;
reserve a,b for expression of C, an_Adj C;
reserve t, t1,t2 for expression of C, a_Type C;
reserve p for FinSequence of QuasiTerms C;
reserve e for expression of C;
reserve a,a9 for expression of C, an_Adj C;

theorem
  for a1,a2 being quasi-adjective of C st Non a1 = Non a2 holds a1 = a2
proof
  let a1,a2 be quasi-adjective of C;
  Non Non a1 = a1 by Th67;
  hence thesis by Th67;
end;
