1. Division of Biostatistics and Bioinformatics; Department of Public Health Sciences; MUSC; 135 Cannon Street Suite 303, MSC 835 Charleston SC 29425-8350 USA
2. Interuniversity Institute for Biostatistics and Statistical Bioinformatics; Hasselt University; Martelarenlaan 42 Hasselt BE3500 Belgium
3. Department of Community and Family Health; University of South Florida; 13201 Bruce B. Downs Blvd, MDC 56 Tampa FL 33612 USA