@inbook{Heckman1982,
author = {Heckman, J.J. and Singer, B.S.},
title= {Population Heterogeneity in Demographic Models},
year = {1982},
doi = {10.1016/B978-0-12-435640-5.50018-3},
editor = {Land, K.C.},
editor = {Rogers, A.},
booktitle = {Multidimensional Mathematical Demography},
address = {New York},
publisher = {Academic Press},
pages = {567--599},
}