Source - Valve Developer Community

Valve wants to make Source 2 engine free for all devs

Getting Started - Valve Developer Community

Steam devs speak: Maximum profits for Valve, minimum responsibilities - Polygon

Valve Source GIF - Valve Source Commentary - Discover & Share GIFs

How To Create Texture Mods for TF2 - Lesson 2.6 Valve Developer Wiki

Positions of entities aren't updated in func_instance · Issue #117 · ValveSoftware/source-sdk-2013 · GitHub

3D Model - Valve Developer Community

Intro to Source Mapping: Creating Entities

Source (game engine) - Wikipedia

Valve Hammer Editor, Half-Life Wiki

How To Compile Source Engine Mod SDK 2013