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  The Klein Bottle - YouTube

  https://www.youtube.com/watch?v=E8rifKlq5hc

  The Klein Bottle is a surface on which you can move from outside to inside without crossing an edge. This shows that inside and outside are not universal con...

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  Magisches Quadrat

  http://www.mathematische-basteleien.de/magquadrat.htm

  Keine Beschreibung vorhanden.

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  Category:Cube – Wikimedia Commons

  https://commons.wikimedia.org/wiki/Category:Cube?uselang=de

  Keine Beschreibung vorhanden.

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