Quattrocchi, Umberto (2012). CRC World Dictionary of Medicinal and Poisonous Plants. Boca Raton, Florida: CRC Press, Taylor & Francis Group. p. 2832. ISBN978-1-4200-8044-5. OCLC971529928.
Ackerfield, Jennifer (2015). Flora of Colorado (First ed.). Fort Worth, Texas: Botanical Research Institute of Texas Press. p. 591. ISBN978-1-889878-45-4. OCLC910162216.