(** * Group II Order *)
Instance incidentp_Proper (A:Tpoint) :
Proper (EqP ==>iff) (IncidentP A).

(** There is only one plane going through three non collinear points. *)
Lemma axiom_plane_uniqueness : forall A B C p q, ~ Col_H A B C ->
IncidentP A p -> IncidentP B p -> IncidentP C p ->
IncidentP A q -> IncidentP B q -> IncidentP C q ->
p =p= q.