@article{Conley2011,
author = {Conley, T.G. and Taber, C.R.},
title= {Inference with ‘difference in differences’ with a small number of policy changes},
year = {2011},
doi = {10.1162/REST_a_00049},
journal = {Review of Economics and Statistics},
volume = {93},
number = {1},
pages = {113--125},
}