@misc{Carstensen2012,
author = {Carstensen, B.},
title= {Epi: A package for statistical analysis in epidemiology},
year = {2012},
URL = {http://cran.r-project.org/web/packages/Epi/index.html},
note = {(accessed January 16, 2013)},
edition = {1.1.40},
}