1. School ofPublic Health; Yale University; New Haven; CT; USA
2. Department of Statistics and Actuarial Science; University of Iowa; Iowa; IA; USA
3. Department of Mathematics; University of West Georgia; Carrollton; GA; USA
4. Department of Clinical Sciences; UT Southwestern Medical Center; Dallas; TX; USA
5. Department of Statistics; Xiamen University; Xiamen; Fujian; China