intro.
induction l as [| a l Hrecl].
simpl in |- *.
auto.
simpl in |- *.
intros.
apply Hrecl.
eapply In_list_remove1.
apply H.
Qed.

Lemma freeVarClosed :
forall (x : fol.Formula L) (v : nat), ~ In v (freeVarFormula (close x)).