Cofactors with human papillomavirus in a population-based study of vulvar cancer. - Madeleine,M.M.; Daling,J.R.; Carter,J.J.; Wipf,G.C.; Schwartz,S.M.; McKnight,B.; Kurman,R.J.; Beckmann,A.M.; Hegensee,M.E.; Galloway,D.A. (J Natl Cancer Inst, 1997)