@article{Nierste:2017oZ,
  author = "Nierste, Ulrich",
  title = "{Penguin pollution in $\beta$ and $\beta_s$}",
  doi = "10.22323/1.291.0081",
  journal = "PoS",
  year = 2017,
  volume = "CKM2016",
  pages = "081"
}