[1] UNIV N CAROLINA,DEPT MED,CHAPEL HILL,NC 27514
[2] UNIV N CAROLINA,DEPT BIOSTAT,CTR COLLABORAT STUDIES COORDINATING,CHAPEL HILL,NC 27514
[3] STANFORD UNIV,STANFORD CTR RES DIS PREVENT,STANFORD,CA 94305
[4] UNIV CALIF SAN DIEGO,DEPT COMMUNITY & FAMILY MED,DIV EPIDEMIOL,LA JOLLA,CA 92093