The Secrets & Science of Primitive Archery book can be ordered at this link.
https://gillsprimitivearchery.com/product/the-secrets-and-science-of-primitive-archery-book/
Ryan Gill builds a sinew bowstring while explaining the process and giving major detailed information on the making and use of other primitive strings as well. Ryan uses these strings to hunt everything from bunnies to bison in many of his primitive hunting videos.