1. The !Kung San: men, women and work in a foraging society;Lee,1979
2. Nisa: the life and words of a !Kung woman;Shostak,1981
3. Nursing frequency, gonadal function, and birth spacing among !Kung hunter-gatherers;Konner;Science,1980
4. Fertility after childbirth: post-partum ovulation and menstruation in bottle and breast feeding mothers;Howie;Clin Endocrinol,1982
5. Global strategy for infant and young child feeding. The optimal duration of exclusive breastfeeding;World Health Organization,2001