Source: Bache, K. & Lichman, M. (2013). UCI Machine Learning Repository [http://archive.ics.uci.edu/ml]. Irvine, CA: University of California, School of Information and Computer Science.
Original source: University Hospital, Zurich, Switzerland: William Steinbrunn, M.D. and University Hospital, Basel, Switzerland: Matthias Pfisterer, M.D.