Chappelka, Arthur H., Howard S. Neufeld, Alan W. Davison, Greg L. Somers, and James R. Renfro. "Ozone Injury on Cutleaf Coneflower (Rudbeckia laciniata) and Crown-Beard (Verbesina occidentalis) in Great Smoky Mountains National Park." Environmental Pollution 125, no. 1 (2003): 53-59.