Shading Fundamentals / Drawing with Dramatic Light and Shadow

Pencil shading techniques: 5 expert tips

Mastering Pencil Shading: A Comprehensive Guide

A Beginner's Tutorial On Applying Light And Shadow In Art

Proko - The Shading Course – Fundamentals of Realism, Light & Shadow

What's the best way to learn and practice portrait shading to help reveal form? - Quora

Shading & Perspective How to Create Depth in Your Drawings

Shading Fundamentals / Drawing with Dramatic Light and Shadow, Brent Eviston

Guide to Drawing Shadows

The Art and Science of Drawing: Learn to Observe, Analyze, and Draw Any Subject (Paperback)