# Media credits for BGK Unit 2 {#agc-bgk-media-credits-unit-02}

Course source: **Kurs:Bündel, Garben und Kohomologie (Osnabrück 2019-2020)**, Kurs:Bündel, Garben und Kohomologie (Osnabrück 2019-2020)/Vorlesung 2. The three substantive media positions retain their Commons identities and component licences. The two official PDFs are authority witnesses, not additional reader media positions.

1. **Illustration of the hairy ball theorem** — [File:Hairy ball one pole.jpg](https://commons.wikimedia.org/wiki/File:Hairy_ball_one_pole.jpg); creator/attribution: RokerHRO; licence/rights status: [CC BY-SA 3.0](https://creativecommons.org/licenses/by-sa/3.0).
   Alternative text: A hairy ball with one swirl at a pole, illustrating that a continuous tangent vector field on the sphere must have a zero.

2. **Inclusion–exclusion diagram for three sets** — [File:Inclusion-exclusion.svg](https://commons.wikimedia.org/wiki/File:Inclusion-exclusion.svg); creator/attribution: Burn~commonswiki (named in the course source; Commons metadata records the creator as 'Unknown Unknown' and the uploader as Chris-martin); licence/rights status: Public domain.
   Alternative text: Diagram of three mutually intersecting circular sets, with each intersection region distinguished by colour.
   Rights note: The inline Wikiversity label is CC-by-sa 3.0; the frozen Commons metadata offers Public domain. Reuse in this edition follows that Commons option.

3. **Animation of a crab on a Möbius strip** — [File:Fiddler crab mobius strip.gif](https://commons.wikimedia.org/wiki/File:Fiddler_crab_mobius_strip.gif); creator/attribution: Hamishtodd1; licence/rights status: [CC BY-SA 4.0](https://creativecommons.org/licenses/by-sa/4.0). The original animation is retained for HTML; a deterministically selected first frame is used for PDF.
   Alternative text: Animation of a crab walking once around a Möbius strip and returning with its orientation reversed.