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