Simon Roper | Livestock in Early Medieval England @simonroper9218 | Uploaded August 2021 | Updated October 2024, 1 day ago.
Banham, D. & Faith, R. 2014. Anglo-Saxon Farms & Farming. Oxford and New York: Oxford University Press.

A bit about hefting on the Lake District website: lakesworldheritage.co.uk/blog/2020/april/02/what-is-hefting

The Ryder paper on breeds: jstor.org/stable/40273081?seq=1#metadata_info_tab_contents