Quake 3 Internals

ioQuake3 github: https://github.com/ioquake/ioq3
http://wiki.ioquake3.org/Entities
Quake 3 Source Code Review: http://fabiensanglard.net/quake3/
Quake III Arena Game Structures: http://caia.swin.edu.au/reports/110209A/CAIA-TR-110209A.pdf
book: https://www.amazon.com/Focus-Programming-Quake-Premier-Development/dp/193184156X

Networking

Game Networing Techniques: http://www.gdcvault.com/play/1022195/Physics-for-Game-Programmers-Networking