Peipert JF, Redding CA, Blume JD, Allsworth JE, Matteson KA, Lozowski F, Mayer KH, Morokoff PJ, Rossi JS. Tailored intervention to increase dual-contraceptive method use: a randomized trial to reduce unintended pregnancies and sexually transmitted infections. Am J Obstet Gynecol. 2008 Jun; 198(6):630.e1-8.