Datta SD, Koutsky LA, Ratelle S, Unger ER, Shlay J, McClain T, Weaver B, Kerndt P, Zenilman J, Hagensee M, Suhr CJ, Weinstock H. Human papillomavirus infection and cervical cytology in women screened for cervical cancer in the United States, 2003-2005. Ann Intern Med. 2008 Apr 01; 148(7):493-500.