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

theorem Th4:
  q => ( p 'or' q ) in TAUT(A)
proof
  q => ( 'not' p => q ) in TAUT(A) by LUKASI_1:5;
  hence thesis by Lm1;
end;
