1. Bone and Breast Density Research Group; Department of Radiology; University of California; San Francisco San Francisco CA USA
2. California Pacific Medical Center Research Institute; San Francisco; CA USA
3. Department of Epidemiology; Graduate School of Public Health; University of Pittsburgh; Pittsburgh PA USA
4. Laboratory of Epidemiology and Population Sciences; National Institute on Aging; Bethesda MD USA
5. Department of Health Sciences; VU University Amsterdam; Amsterdam The Netherlands
6. Department of Epidemiology and Biostatistics; VU University Medical Center; Amsterdam The Netherlands
7. Department of Preventive Medicine; University of Tennessee Health Science Center; Memphis TN USA