Archived plex documentation: https://web.archive.org/web/20150107154037/http://dev.plexapp.com/docs/index.html
Metadata models: https://web.archive.org/web/20150113085312/http://dev.plexapp.com/docs/agents/models.html
Plugin development walkthrough: https://forums.plex.tv/t/plex-plugin-development-walkthrough/9909
Plex framework documentation in pdf: https://aws1.discourse-cdn.com/plex/original/3X/f/0/f0371b016d94dcbe6fca92d2bb13c9b4d685ae04.zip
Plex media api in doc: https://aws1.discourse-cdn.com/plex/original/3X/b/e/beb88d4e77d0ba2546495fb4c7e84b5996fff45e.zip
Trailer metadata: https://forums.plex.tv/t/correct-way-to-add-trailers-to-movie/360564/5
Plex missing from dev docs: https://docs.google.com/document/d/1MyhhTsg5xdDD5LRbOZ5x5QxkmEyXv6rB-22Z7tdpy34/edit