1. Veterans Affairs Medical Center, Washington, DC, USA
2. George Washington University, Washington, DC, USA
3. Georgetown University, Washington, DC, USA
4. MedStar Washington Hospital Center, Washington, DC, USA
5. University of Alabama at Birmingham, Birmingham, AL, USA
6. University of California, Los Angeles, CA, USA
7. Weschester Medical Center, Valhalla, NY, USA
8. New York Medical College, Valhalla, NY, USA