1. Department of Biostatistics; Indiana University Fairbanks School of Public Health and School of Medicine; Indianapolis, Indiana 46202 U.S.A.
2. Department of Mathematics; Shanghai Jiao Tong University; Shanghai 200240 China
3. Biostatistics & Data Sciences Asia; Boehringer Ingelheim (China) Investment Co., Ltd.; Shanghai 200040 China
4. Department of Biostatistics; Indiana University School of Medicine and Fairbanks School of Public Health; Indianapolis, Indiana 46202 U.S.A.