References
- Bischoff F. J. Americ. Pharm. Assn. 1924; 13: 898–901
- Culter S. H. Echinacea, a phytochemical study. 1931; 27, Bull. Univ. Wisconsin, Serial No. 1787
- Heukels H. De Flora van Nederland. Leiden 1910; III
- Heyl, Hart. J. Amer. Chem. Soc. 1915; 37: 1769
- Hoppe H. A. Drogenkunde. Hamburg 1941
- Hunnius C. Pharmazeutisches Wörterbuch. Berlin 1955
- Jacobs M. L., Burlage H. M. Index of plants of North Carolina. Chapel Hill 1958
- Level C. F. Cinquefoil. London, (sine dato)
- Niederkorn J. S. Echinacea in the treatment of the bites of venomous serpents. Cincinnati, Ohio 1910; 16
- Potter's Cyclopaedia of botanical drugs and preparations. London 1941
- Sipkes C. Flora van onze gekweekte kruidachtige vollegrondsgewassen. Zutphen (Holland) 1922
- Steinmetz E. F. Materia Medica Vegetabilis. Amsterdam 1954
- Steinmetz E. F. Drug Guide. Amsterdam 1959
- Steinmetz E. F. Codex Vegetabilis. Amsterdam 1957