Case number 28

Klein bottle (cut in half) Boy's surface of degree 6 Klein bottle Two-sided surface with the clover leaf sling as boundary curve
Möbius strip Clover leaf sling on torus Clover leaf sling on torus Model of a clover leaf sling with singularity-free surface
3-times twisted Möbius strip with clover leaf sling as border Three Möbius strips Three Möbius strips Three Möbius strips
Wooden ring with 7 neighbouring areas Wooden ring with 7 neighbouring areas Three rings that are devoured with each other, but not pairwise

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