1. Department of Biostatistics and Epidemiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, U.S.A.
yuanpeic@sas.upenn.edu
2. Center for Statistical Science, School of Mathematical Sciences, Peking University, 5 Yiheyuan Road, Beijing 100871, China
weilin@math.pku.edu.cn
3. Department of Biostatistics and Epidemiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, U.S.A.
hongzhe@upenn.edu