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
  X|- p implies X|- q => p
proof
  assume
A1: X|- p;
  X|- p => (q => p) by CQC_THE1:59;
  hence thesis by A1,CQC_THE1:55;
end;
