Excessive daytime sleepiness in Parkinson disease: Is it the drugs or the disease?

Gjerstad, M. D., Alves, G., Wentzel-Larsen, T., Aarsland, D., & Larsen, J. P. (2006). Excessive daytime sleepiness in Parkinson disease: Is it the drugs or the disease. Neurology, 67(5), 853-858.