Drawing on the Right Side of the Brain: The Definitive, 4th Edition
Art Before Breakfast: A Zillion Ways to be More Creative No Matter How Busy You Are
The Sketchnote Handbook: the illustrated guide to visual note taking
Ed Emberley's Drawing Book: Make a World
Quick Sketching with Ron Husband
Fast Sketching Techniques: Capture the Fundamental Essence of Elusive Subjects