1. School of Medicine, Duke University, Durham, NC, USA,
2. Agency for Toxic Substances and Disease Registry, National ALS Registry, Atlanta, GA, USA,
3. Department of Neurology, University Medical Center Utrecht, Utrecht, The Netherlands,
4. Department of Neurology, Geisel School of Medicine at Dartmouth, Hanover, NH, USA,
5. Department of Neurology, Tel-Aviv Medical Center, Tel-Aviv, Israel, and
6. Department of Neurology, Duke University and Durham VA Medical Center, Durham, NC, USA