1. Center for Clinical Epidemiology and Biostatistics, Department of Biostatistics and Epidemiology, Perelman School of Medicine; University of Pennsylvania; Philadelphia; PA; USA
2. Department of Global Pharmacovigilance and Epidemiology; Bristol-Myers Squibb; Hopewell; NJ; USA
3. Department of Global Epidemiology; AstraZeneca Pharmaceuticals LP; Wilmington; DE; USA
4. Department of Medicine, Perelman School of Medicine; University of Pennsylvania; Philadelphia; PA; USA
5. Department of Safety and Epidemiology; HealthCore, Inc.; Wilmington; DE; USA
6. General Practice Research Database; Medicines and Healthcare Products Regulatory Agency; London; UK
7. Depatment of Medical Research; Cegedim Strategic Data Medical Research; London; UK