Planet Wild - Mission 18
- https://animaldiversity.org/accounts/Athene_noctua/
- https://www.uni-kiel.de/Agraroekonomie/Abteilungen/marktlehre/research/download/The evolving farm structure.pdf
- https://digitalcommons.usf.edu/cgi/viewcontent.cgi?article=2426&context=jrr