References
- Fleissig , A. 1991 . Unintended pregnancies and the use of contraception: changes from 1984 to 1989 . British Medical Journal , 302 : 147
- Office of Population Censuses and Surveys . 1991 . World population: trends and projections . Population Trends , 63 : 36 – 39 .
- Potts , M. and Rosenfield , A. 1990 . The fifth freedom revisited: I. Background and existing programmes . Lancet , 336 : 1227 – 1231 .