TY - JOUR A1 - Frost, J.J. A1 - Singh, S. A1 - Finer, L.B. T1 - Factors Associated with Contraceptive Use and Nonuse, United States, 2004 Y1 - 2007 DO - 10.1363/3909007 JF - Perspectives on Sexual and Reproductive Health VL - 39 ER -