Dodel R, Jönsson B, Reese JP, Winter Y, Martinez-Martin P, Holloway R, Sampaio C, Ružicka E, Hawthorne G, Oertel W, Poewe W, Stebbins G, Rascol O, Goetz CG, Schrag A. Measurement of costs and scales for outcome evaluation in health economic studies of Parkinson's disease. Mov Disord. 2014 Feb; 29(2):169-76.