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 => q) => r is valid implies q => r is valid
proof
  assume
A1: (p => q) => r is valid;
  ((p => q) => r) => (q => r) is valid;
  hence thesis by A1,CQC_THE1:65;
end;
