1. Pain Management Centers of America, Paducah, KY & Evansville, IN, USA
2. University of Illinois at Urbana-Champaign, College of Liberal Arts and Sciences, Champaign, IL, USA
3. Advocate Illinois Masonic Medical Center and College of Medicine, University of Illinois, Chicago, IL, USA
4. LSU Health Sciences Center, Shreveport, Ochsner Shreveport Hospital and Pain Clinic Feist-Wieller Cancer Center, Shreveport, LA, USA
5. Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA