Robertson, S., & Bertling, T. How to draw: Drawing and sketching objects and environments from your imagination.
Chicago-referens (17:e uppl.)Robertson, Scott, och Thomas Bertling. How to Draw: Drawing and Sketching Objects and Environments from Your Imagination.
MLA-referens (8:e uppl.)Robertson, Scott, och Thomas Bertling. How to Draw: Drawing and Sketching Objects and Environments from Your Imagination.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.