1. Department of Neurology, Jefferson Headache Center, 111 South 11th Street, Ste. 8130, Philadelphia, PA 19107-5092, USA
2. Departments of Neurology, Epidemiology, and Social Medicine, Montefiore Headache Unit, Albert Einstein College of Medicine, Bronx, New York, USA
3. Innovative Medical Research, Stamford, CT, USA