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Binns et al 2001. Binns, Shannon E.; Baum, Bernard R.; Arnason, John T. (2001). "Typification of Echinacea purpurea (L.) Moench (Heliantheae: Asteraceae) and its implications for the correct naming of two Echinacea taxa". Taxon. 50 (4): 1169–1175. doi:10.2307/1224737. JSTOR1224737.
Binns et al 2002. Binns, Shannon E.; Baum, Bernard R.; Arnason, John Thor (2002). "A Taxonomic Revision of Echinacea (Asteraceae: Heliantheae)". Systematic Botany. 27 (3): 610–632. JSTOR3093966.