. Author manuscript; available in PMC: 2016 Apr 21.
Published in final edited form as: Artif Intell Med. 2016 Jan 16;67:75–93. doi: 10.1016/j.artmed.2016.01.002
This manuscript version is made available under the CC-BY-NC-ND 4.0 license: http://creativecommons.org/licenses/by-nc-nd/4.0/