@article{whysyntheticcontrolestimatorsarebiased,
  title = {Why Synthetic Control estimators are biased and what to do about it: Introducing Relaxed and Penalized Synthetic Controls},
  author = {Oscar Engelbrektson},
  year = {2021},
  eprint = {2111.10784},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2111.10784v1},
}