1. Division of Oncology, Department of Medicine, Stanford University School of Medicine, 269 Campus Drive, Stanford, CA 94305
2. Department of Statistics, the Wharton School, University of Pennsylvania, 3730 Walnut Street, Philadelphia, PA 18014
3. School of Mathematics and Physics, University of Science and Technology Beijing, 30 Xueyuan Road, Haidian District, Beijing 100083 P. R. China
4. Stanford Genome Technology Center, Stanford University, 3165 Porter Drive, Palo Alto, CA 94304