For further research on logo design:
Adams, Sean, Noreen Morioka and Terry Stone. Logo
Design Workbook. Glucester: Rockport Publishers, Inc., 2004.
Thomas, Gregory. How to Design Logos, Symbols and Icons. Cincinnati: How Design Books, 2000.
Links to more information about pictorial symbols:
The Heraldy Society of Scotland: Heraldic Design
Petroglyphs and Pictoglyphs: Petroglyphs.us
University of Virginia: The Mayan Epigraphic Database Project
University of Pennsylvania Museum of Archaeology and Anthropology: Egypt, A new look at an ancient culture
NTIEVA Newsletter, Sifting Through the Sands of Time with Egyptian and Mayan Art