License
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- Attribution 4.0 (CC BY 4.0)19
- Attribution-NonCommercial 4.0 (CC BY-NC 4.0)5
- Attribution 3.0 United States3
- Attribution-ShareAlike 4.0 (CC BY-SA 4.0)3
- Attribution-NonCommercial-NoDerivatives 4.0 (CC BY-NC-ND 4.0)2
- Attribution-NonCommercial-NoDerivs 3.0 United States2
- CC0 1.0 Universal2
- Public Domain Mark 1.02