@article{Boegli:2012vX,
  author = "Boegli, Michael  and  Niedermayer, Ferenc  and  Pepe, Michele  and  Wiese, Uwe-Jens",
  title = "{Study of $\theta$-Vacua in the 2-d $O(3)$ Model}",
  doi = "10.22323/1.164.0228",
  journal = "PoS",
  year = 2012,
  volume = "Lattice 2012",
  pages = "228"
}