@article{selectionandparalleltrends,
  title = {Selection and parallel trends},
  author = {Dalia Ghanem and Pedro H. C. Sant'Anna and Kaspar Wüthrich},
  year = {2022},
  eprint = {2203.09001},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2203.09001v9},
}