1. American Herbal Pharmacopoeia. 2010a. Echinacea angustifolia Root: Standards of analysis, quality control, and therapeutics. Scotts Valley, CA: American Herbal Pharmacopoeia and Therapeutic Compendium.
2. ———. 2010b. Echinacea pallida root: Standards of analysis, quality control, and therapeutics. Scotts Valley, CA: American Herbal Pharmacopoeia and Therapeutic Compendium.
3. Barnes, J., L.A. Anderson, S. Gibbons, and J.D. Phillipson. 2005. Echinacea species (Echinacea angustifolia (DC.) Hell. Echinacea pallida (Nutt.) Nutt., Echinacea purpurea (L.) Moench): a review of their chemistry, pharmacology and clinical properties. The Journal of Pharmacy and Pharmacology 57(8): 929–954.
4. Bauer, R., P. Remiger, and H. Wagner. 1988. Alkamides from the roots of Echinacea purpurea. Phytochemistry 21(7): 2339–2342.
5. Bauer, R., P. Remiger, and H. Wagner. 1988b. Echinacea Part 3. Comparative TLC and HPLC analysis of herbal drugs from Echinacea purpurea, E. pallida and E. angustifolia. Deutsche Apotheker-Zeitung 128(4): 174–180.