Sant'Anna P, Zhao J (2020). “Doubly Robust Difference-in-Differences Estimators.” Journal of Econometrics, 219, 101-122. https://doi.org/10.1016/j.jeconom.2020.06.003.

@Article{,
  title = {Doubly Robust Difference-in-Differences Estimators},
  author = {Pedro H. C. Sant'Anna and Jun Zhao},
  journal = {Journal of Econometrics},
  year = {2020},
  volume = {219},
  pages = {101-122},
  url = {https://doi.org/10.1016/j.jeconom.2020.06.003},
}