reserve A for QC-alphabet;
reserve sq for FinSequence,
  x,y,z for bound_QC-variable of A,
  p,q,p1,p2,q1 for Element of QC-WFF(A);
reserve s,t for bound_QC-variable of A;

theorem
  All(x,y,z,p) = All(t,q) implies x = t & All(y,z,p) = q by Th5;
