https://en.wikipedia.org/wiki/Manifold#/media/File:Klein_bottle.svg

https://en.wikipedia.org/wiki/Real_projective_plane#/media/File:SelfIntersectingDisk.PNG

http://www.imaginary-exhibition.com/mpe2013/MPE2013/module-stereographic-projection.html

https://en.wikipedia.org/wiki/Manifold#/media/File:BoysSurfaceTopView.PNG

https://en.wikipedia.org/wiki/Curvature_of_Riemannian_manifolds#/media/File:Gaussian_curvature.svg

https://en.wikipedia.org/wiki/Genus_(mathematics)#/media/File:Double_torus_illustration.png

https://en.wikipedia.org/wiki/Vector_field#/media/File:Vector_sphere.svg

https://en.wikipedia.org/wiki/Genus_(mathematics)#/media/File:Triple_torus_illustration.png