reserve A for QC-alphabet;
reserve p, q, r, s, t for Element of CQC-WFF(A);
reserve X for Subset of CQC-WFF(A);

theorem
  (p => 'not' p) => 'not' p in TAUT(A)
proof
  ('not' 'not' p => 'not' p) => 'not' p in TAUT(A) & (p => 'not' p) => ('not'
  'not' p => 'not' p) in TAUT(A) by Th28,CQC_THE1:42;
  hence thesis by Th3;
end;
