↑ Gatto. Exploring Visual Design: The Elements and Principles. m/s. 122–123.
Sumber
Gatto, Porter, and Selleck. Exploring Visual Design: The Elements and Principles. 3rd ed. Worcester: Davis Publications, Inc., 2000. ISBN0-87192-379-3
Stewart, Mary, Launching the imagination: a comprehensive guide to basic design. 2nd ed. New York: The McGraw-Hill Companies, Inc., 2006. ISBN0-07-287061-3
