Sesquiterpene Lactones in Arnica montana: a Rapid Analytical Method and the Effects of Flower Maturity and Simulated Mechanical Harvesting on Quality and Yield - Douglas, James A; Smallfield, Bruce M; Burgess, Elaine J; Perry, Nigel B; Anderson, Rosemary E; Douglas, Malcolm H; Glennie, V leAnne (Planta Medica, 2004)