"Genus: Clematis L."Germplasm Resources Information Network. United States Department of Agriculture. 2000-12-20. Archived from the original on 2009-06-17. Retrieved 2011-02-02.
"Genus: Clematis L."Germplasm Resources Information Network. United States Department of Agriculture. 2000-12-20. Archived from the original on 2009-06-17. Retrieved 2011-02-02.