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
  |- TAUT(A)
  proof
A1:  |- TAUT(A) iff {}(CQC-WFF(A)) |- TAUT(A) by Th15;
    {}(CQC-WFF(A)) |- TAUT(A) by Th13;
    hence thesis by A1;
  end;
