Determination of minimal important difference thresholds for Parkinson's disease questionnaire-39 in advanced Parkinson's disease patients. (January 2016) - Antonini, Angelo; Bacci, Elizabeth Dansie; Sail, Kavita; Jalundhwala, Yash J.; Kandukuri, Prasanna L.; Marshall, Thomas; Chatamra, Krai; Wiklund, Ingela; Revicki, Dennis