1. University of Iowa; Iowa City IA USA
2. Alliance Statistics and Data Center; Duke University Medical Center; Durham NC USA
3. Minneapolis Veterans Administration Medical Center; University of Minnesota; Minneapolis MN USA
4. University of Chicago; Chicago IL USA
5. Wake Forest University School of Medicine; Winston Salem NC USA
6. The Norris Cotton Cancer Center and Geisel School of Medicine at Dartmouth; Lebanon NH USA
7. Washington University School of Medicine; St Louis MO USA