https://docs.freebsd.org/en/books/porters-handbook/
FreeBSD Porter's Handbook | FreeBSD Documentation Portal
Essential reading if you plan on providing a port of a third party piece of software
handbook documentation portal
https://docs.factorcode.org/content/article-handbook.html
Factor handbook - Factor Documentation
handbook documentationfactor
https://docs.FreeBSD.org/en/books/handbook/
FreeBSD Handbook | FreeBSD Documentation Portal
A constantly evolving, comprehensive resource for FreeBSD users
handbook documentation portal