Baker, David M
Freeman, Christopher J
Knowlton, Nancy
Thacker, Robert W
Kim, Kiho
Fogel, Marilyn L
Article History
Received: 15 August 2014
Revised: 23 February 2015
Accepted: 1 April 2015
First Online: 19 May 2015
Competing interests
: The authors declare no conflict of interest.