reserve A for QC-alphabet;
reserve a,b,b1,b2,c,d for object,
  i,j,k,n for Nat,
  x,y,x1,x2 for bound_QC-variable of A,
  P for QC-pred_symbol of k,A,
  ll for CQC-variable_list of k,A,
  l1 ,l2 for FinSequence of QC-variables(A),
  p for QC-formula of A,
  s,t for QC-symbol of A;
reserve Sub for CQC_Substitution of A;

theorem
  for p being QC-formula of A st p is conjunctive holds Bound_Vars(p) = (
  Bound_Vars(the_left_argument_of p)) \/ ( Bound_Vars(the_right_argument_of p))
  by Lm1;
