1. Pain Management Center of Paducah, Paducah, KY, USA
2. Pain Management Center of University of Louisville, Louisville, KY, USA
3. Spine Pain Diagnostics Associates, Niagara, WI, USA
4. Mid Atlantic Spine & Pain Physicians, Newark, DE, and Temple University Hospital, Philadelphia, PA, USA
5. Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA