reserve A for QC-alphabet;
reserve p, q, r, s, p1, q1 for Element of CQC-WFF(A),
  X, Y, Z, X1, X2 for Subset of CQC-WFF(A),
  h for QC-formula of A,
  x, y for bound_QC-variable of A,
  n for Element of NAT;

theorem Th1:
  p in X implies X |- p
proof
  X c= Cn(X) by CQC_THE1:17;
  hence thesis by CQC_THE1:def 8;
end;
