Golovko, E.A., and T.O. Shcherbakova. “Physiological-and-Biochemical Properties of Introduced Species of Echinacea Moench Genus”. Plant Introduction 7 (December 1, 2000): 125-132. Accessed November 5, 2024. http://plantintroduction.org/index.php/pi/article/view/1403.