[1] Division of Epidemiology,
[2] Stanford University School of Medicine,undefined
[3] Stanford,undefined
[4] California,undefined
[5] Kaiser Permanente Medical Care Program,undefined
[6] Division of Research,undefined
[7] Oakland,undefined
[8] California,undefined
[9] Center for Clinical Epidemiology and Biostatistics,undefined
[10] School of Medicine,undefined
[11] University of Pennsylvania,undefined
[12] Philadelphia,undefined
[13] Pennsylvania,undefined
[14] USA,undefined