@article{Hotz1997,
author = {Hotz, V.J. and Mullin, C. and Sanders, S. },
title= {Bounding Causal Effects Using Data from a Contaminated Natural Experiment: Analyzing the Effects of Teenage Childbearing},
year = {1997},
doi = {10.2307/2971732},
journal = {Review of Economic Studies },
volume = {64},
number = {4},
pages = {575−603},
}