1. Institute of Epidemiology and Preventive Medicine; National Taiwan University; Taipei 100 Taiwan
2. Institute of Statistical Science; Academia Sinica; Taipei 115 Taiwan
3. Department of Applied Mathematics; National Chung Hsing University; Taichung 402 Taiwan
4. Yahoo, Sunnyvale; California 94089 U.S.A.
5. Department of Statistics and Bioinformatics Research Center; North Carolina State University; Raleigh, North Carolina 27695 U.S.A.
6. Department of Statistics; National Cheng Kung University; Tainan 701 Taiwan