"Acanthus L."Germplasm Resources Information Network. United States Department of Agriculture. 2009-01-23. Archived from the original on 3 December 2013. Retrieved 2010-06-19.
web.archive.org
"Acanthus L."Germplasm Resources Information Network. United States Department of Agriculture. 2009-01-23. Archived from the original on 3 December 2013. Retrieved 2010-06-19.