@article{econhot_econhot-reading-13,
  title = {On the Role of the Propensity Score in Efficient Semiparametric Estimation of Average Treatment Effects},
  author = {Jinyong Hahn},
  journal = {Econometrica},
  year = {1998},
  volume = {66},
  number = {2},
  pages = {315},
  doi = {10.2307/2998560},
  url = {https://doi.org/10.2307/2998560}
}