1. Epidemiology and Biostatistics Program, School of Public Health, UNLV, Las Vegas, NV, USA
2. Department of Biostatistics and Bioinformatics, Roswell Park Cancer Institute, Buffalo, NY, USA
3. Department of Biostatistics, University at Buffalo, Buffalo, NY, USA
4. Department of Mathematics, Southern University of Science and Technology, Shenzhen, P.R.China