How to Create Custom Textures for the Source Engine – LambdaGeneration
Creating a Material - Valve Developer Community
Getting Around in the Material System | Valve Developer Union
GitHub - NeilJed/VTFLib: VTFLib is a LGPL open source programming library that provides a C and C++ API for reading and writing Valve VTF and VMT format image files.
Textures - Valve Hammer Editor 3.4 Documentation
Steam Community :: Guide :: VTF-File - Create a Texture
Source SDK - Authoring Tools: 6 Common File Types for Level Design in Hammer Source
VTF Explorer [Source Engine] [Modding Tools]
Source SDK: How to create a texture (VMT)
Steam Community :: Guide :: VTF-File - Create a Texture