@inbook{Cohen1993,
author = {Cohen, B. },
title= {Fertility levels, differentials, and trends},
year = {1993},
editor = {Foote, K.A.},
editor = {Hill, K.H.},
editor = {Martin, L.G. },
booktitle = {Demographic change in sub-Saharan Africa},
address = {Washington, D.C.},
publisher = {National Academy Press},
pages = {8--67},
}