Kaufmann H, Norcliffe-Kaufmann L, Palma JA, Biaggioni I, Low PA, Singer W, Goldstein DS, Peltier AC, Shibao CA, Gibbons CH, Freeman R, Robertson D. Natural history of pure autonomic failure: A United States prospective cohort. Ann Neurol. 2017 Feb; 81(2):287-297.