simple induction E'; simple induction E''; simpl in |- *; intros.
elim X1; intros Xl Xr; elim X2; intros y p; elim (Xl y); intros y0 p0;
exists y0; apply EQC_tran with (e y); auto with zfc.
Qed.

(* Specifications: *)
Theorem CINC_refl : forall E : Ens, CINC E E.
unfold CINC in |- *; auto with zfc.
Theorem CINC_refl : forall E : Ens, CINC E E.
unfold CINC in |- *; auto with zfc.