* Vizgirdas, Ray S.; Rey-Vizgirdas, Edna. ''A guide to plants of Yellowstone & Grand Teton national parks: natural history notes and uses'' (en [[anglés]]). University of Utah Press, 2007, p.167 | * Vizgirdas, Ray S.; Rey-Vizgirdas, Edna. ''A guide to plants of Yellowstone & Grand Teton national parks: natural history notes and uses'' (en [[anglés]]). University of Utah Press, 2007, p.167 |