Antonini A, Martinez-Martin P, Chaudhuri RK, Merello M, Hauser R, Katzenschlager R, Odin P, Stacy M, Stocchi F, Poewe W, Rascol O, Sampaio C, Schrag A, Stebbins GT, Goetz CG. Wearing-off scales in Parkinson's disease: critique and recommendations. Mov Disord. 2011 Oct; 26(12):2169-75.