Motivations to use hormonal contraceptive methods and condoms among HIV-positive and negative women randomized to a progestin contraceptive in Malawi: a qualitative study oleh Agatha K. Bula, Kendra Hatfield-Timajchy, John Chapola, L. Chinula, Stacey A. Hurst, Athena P. Kourtis, J. H. Tang