Metz G, Coppard N, Cooper JM, Delatycki MB, D?rr A, Di Prospero NA, Giunti P, Lynch DR, Schulz JB, Rummey C, Meier T. Rating disease progression of Friedreich's ataxia by the International Cooperative Ataxia Rating Scale: analysis of a 603-patient database. Brain. 2013 Jan; 136(Pt 1):259-68.