1. Headache Group-Department of Neurology, University of California, San Francisco, CA, USA
2. Headache Group, NIHR-Wellcome Clinical Research Facility, King’s College London, UK
3. Montefiore Headache Center, Bronx, NY, USA
4. New York Headache Center, New York, NY, USA
5. Clinvest, Headache Care Center, Springfield, MO, USA
6. electroCore LLC, Basking Ridge, NJ, USA