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 Th10:
  (q => (q => r)) => (q => r) in TAUT(A)
proof
  (q => r) => (q => r) in TAUT(A) & ((q => r) => (q => r)) => ((q => (q => r)
  ) => (q => r)) in TAUT(A) by Lm18,Th4;
  hence thesis by CQC_THE1:46;
end;
