Great link found by Eric Poehlsen on this thread:

http://www.nava.org/Flag%20Design/GFBF/index.html

The publication is created by NAVA:

The North American Vexillological Association (NAVA) is dedicated to vexillology, the study of flag history and symbolism. For more information about its activities, publications, and membership, visit www.nava.org or write:
NAVA
1977 N. Olden Ave. Ext., PMB 225,
Trenton, NJ 08618–2193, U.S.A.
ISBN–13: 978–0–9747728–1–3
ISBN–10: 0–9747728–1–X
Designed by Melissa Scott
© 2006 North American Vexillological Association