Patrick Kevin, Griswold William G, Raab Fred, Intille Stephen S
Department of Family and Preventive Medicine, University of California San Diego, La Jolla, California 92093-0811, USA.
Am J Prev Med. 2008 Aug;35(2):177-81. doi: 10.1016/j.amepre.2008.05.001. Epub 2008 Jun 12.