1Shenghui Wu*, 2Zhong Liu, 3Zhaomin Liu and 4Lap Ah Tse*
1University of Texas Health Science Center at San Antonio-Laredo Campus, Department of Epidemiology & Biostatistics, Laredo, TX, USA.
2Vanderbilt University, School of Medicine, Vanderbilt University, Nashville, TN,USA.
3,4School of Public Health and Primary Care, the Chinese University of Hong Kong, Hong Kong SAR, PR China.
E-mail:wus@uthscsa.edu
