Introduction to Shading
Shading tutorial (Very serious stuff) [June 2014 Pop-reel!]
How to Stencil with Shading & Highlighting - Wall Painting Techniques
GRPHICS06 - Shading
Lesson 8: Introduction to Shading Techniques
Shading - Wikipedia
Decorative Painting tutorial: how to shade by floating colors
Hummingbird Arts Studio is a full-service art and design studio
Guide to Shading Techniques: Hatching, Cross-Hatching, Scribbling and Others - Erika Lancaster- Artist + Online Art Teacher
Tutorial - Shading Hair by RaikaiRan on DeviantArt