1.) King's American Dispensatory, 1898, by Harvey Wickes Felter, M.D., and John Uri Lloyd, Phr. M., Ph. D.
2.) Woelkart, K., Koidl, C., Grisold, A., Gangemi, J. D., Turner, R. B., Marth, E., and Bauer, R. Bioavailability and pharmacokinetics of alkamides from the roots of Echinacea angustifolia in humans. J Clin Pharmacol 2005;45(6):683-689.
3.) u, C. and Kitts, D. D. Studies on the antioxidant activity of Echinacea root extract. J Agric Food Chem 2000;48(5):1466-1472
4.) Huntley AL, Thompson Coon J, Ernst E. The safety of herbal medicinal products derived from Echinacea species: a systematic review. Drug Saf 2005;28:387-400.
5.) Woelkart, K., Marth, E., Suter, A., Schoop, R., Raggam, R. B., Koidl, C., Kleinhappl, B., and Bauer, R. Bioavailability and pharmacokinetics of Echinacea purpurea preparations and their interaction with the immune system. Int J Clin Pharmacol Ther 2006;44(9):401-408.