^Darwin, Charles Robert. The Voyage of the Beagle. Vol. XXIX. The Harvard Classics. New York: P.F. Collier & Son, 1909–14; Bartleby.com, 2001. www.bartleby.com/29/ （页面存档备份，存于互联网档案馆） [accessed 30 Sep 2016] Ch VI.
^Bulletin of the Torrey Botanical Club (Torrey Botanical Club, 1887), p. 163
^The Rise of Capitalism on the Pampas: The Estancias of Buenos Aires, 1785-1870, By Samuel Amaral (Cambridge University Press,2002) p. 129
"Charles Darwin, who visited the pampas while traveling around the world, refers to Cynara cardunculus as cardoon, differentiating it from the great thistle, which scientific designation does not mention, described by F. B. Head. The former was as high as a horse; the second, higher than the head of a horserider. In Far Away and Long Ago, William Henry Hudson mentions two types: the cardoon thistle, or wild artichoke, of a bluish or grey-greenish color, and the giant thistle, cardo asnal for the natives and Carduus marianum for botanists, with white and green leaves."
^JW, Kendrick; J, Tucker; SA, Peoples. Nitrate poisoning in cattle due to ingestion of variegated thistle, Silybum marianum.. Journal of American Veterinary Medicine Association. 1955, 126 (934): 53–56. PMID 13221510.