1. McGregor, R. L. The taxonomy of the genus Echinacea (Compositae). Univ. Kansas Sci. Bul 48, 113–142 (1968).
2. Lindstrom, A., Ooyen, C., Lynch, M., Blumenthal, M. & Kawa, K. Sales of herbal dietary supplements increase by 7.9% in 2013, marking a decade of rising sales: turmeric supplements climb to top ranking in natural channel. HerbalGram 103, 52–56 (2014).
3. Smith, T. et al. Herbal dietary supplement sales in US increase 6.8% in 2014. HerbalGram 107, 52–59 (2015).
4. Taylor, J. A. et al. Efficacy and safety of Echinacea in treating upper respiratory tract infections in children: a randomized controlled trial. Jama 290, 2824–2830 (2003).
5. Tierra, M. Echinacea: an effective alternative to antibiotics. J. Herb. Pharmacother 7, 79–89 (2008).