1. Leon Levine Hall of Medical Sciences, School of Osteopathic Medicine, Campbell University, 4350 US Hwy 421 S, Lillington, NC 27546, USA
2. College of Medicine, University of Illinois, 1601 Parkview Ave., Rockford, IL 61107, USA
3. Lake Erie College of Osteopathic Medicine at Seton Hill, Lynch Hall, 20 Seton Hill Dr, Greensburg, PA 15601, USA
4. College of Medicine, University of Florida, 1600 SW Archer Rd., Gainesville, FL 32610, USA
5. Department of Neurological Surgery, University of Kansas Medical Center, 2060 W 39th Ave., Kansas City, KS 66160, USA
6. Department of Orthopedic Surgery, College of Medicine, University of Arizona, 1501 N Campbell Ave., Tucson, AZ 85724, USA
7. Department of Neurosurgery, University of Florida, 1600 SW Archer Rd., Gainesville, FL 32610, USA