Wheatgrass, Superfood for a New Millennium, by Li Smith, Vital Health Publishing, ISBN 1-890612-10-3. www.vitalhealth.net
The classic book on the subject is, The Wheatgrass Book by Ann Wigmore, Avery Publishing, ISBN 0-89529-234-3.
In Wigmore's book, she says to plant "hard" or "winter" wheatberries. The grain is small, elongated, and deep golden brown. I think it's pretty available at health food stores