Affiliation: | 1. Department of Epidemiology, University of Michigan, Ann Arbor, MI 48109, United States;2. Department of Mathematics, University of Michigan, Ann Arbor, MI 48109, United States;3. Department of Mathematics, University of Central Florida, Orlando, FL 32816, United States;4. Department of Mathematics, Ohio State University, Columbus, OH 43210, United States;5. Department of Mathematics and Statistics, University of Victoria, Victoria, BC V8W 3R4, Canada |