http://vm.cfsan.fda.gov/~dms/ds-tryp1.html

http://www.thewayup.com/products/0358.cfm

http://www.cocoonnutrition.org/catalog/page_tryptophan.php

http://www.iherb.com/ProductsList.aspx?c=1&cid=1581

http://www.raysahelian.com/tryptophan.html

http://www.nutrovita.com/store/l-tryptophan.htm

http://en.wikipedia.org/wiki/Tryptophan

http://www.fth-inc.com/tryptophan.htm

http://health-and-beauty.become.com/l-tryptophan?kd=870733&tc=12

http://www.transformyourhealth.com/miscprods/ltryptophan.htm