reserve A for QC-alphabet;
reserve X,T for Subset of CQC-WFF(A);
reserve F,G,H,p,q,r,t for Element of CQC-WFF(A);
reserve s,h for QC-formula of A;
reserve x,y for bound_QC-variable of A;
reserve f for FinSequence of [:CQC-WFF(A),Proof_Step_Kinds:];
reserve i,j for Element of NAT;

theorem
  not x in still_not-bound_in All(x,y,s) & not y in still_not-bound_in
  All(x,y,s)
proof
  not y in still_not-bound_in All(y,s) by Th5;
  then
A1: not y in still_not-bound_in All(x,All(y,s)) by Th5;
  not x in still_not-bound_in All(x,All(y,s)) by Th5;
  hence thesis by A1,QC_LANG2:14;
end;
