This image was acquired from
wikimedia. It was marked as Public Domain or CC0 and is free to use. To verify, go to the source and check the information there.
Keywords from Image Description:
KleinBottleAsSquare.svg The fundamental polygon of Klein bottle To construct the Klein bottle join the sides with the same letter together so that the directions of the arrows match This cannot be done in three dimensions without the surface intersecting itself Ilmari Karonen en Fundamental polygon Klein bottle