Require Export GeoCoq.Elements.OriginalProofs.lemma_collinearorder.
Require Export GeoCoq.Elements.OriginalProofs.lemma_outerconnectivity.
Section Euclid.
Context `{Ax:euclidean_neutral_ruler_compass}.

(* Specifications: *)
Lemma lemma_collinear4 :
forall A B C D,
Col A B C -> Col A B D -> neq A B ->
Col B C D.