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 Th62:
  for a being non positive expression of C, an_Adj C
  holds (non_op C)term (Non a) = a
proof
  let a be non positive expression of C, an_Adj C;
  ex a9 being expression of C, an_Adj C st ( a = (non_op C)
  term a9)&( Non a = a9) by Th60;
  hence thesis;
end;
