@inproceedings{Zimmermann:2015tO,
  author = "Zimmermann, Frank",
  title = "{Future Highest-Energy Circular Colliders}",
  doi = "10.22323/1.231.0032",
  booktitle = "Proceedings of Proceedings of the Corfu Summer Institute 2014  {\textemdash} PoS(CORFU2014)",
  year = 2015,
  volume = "231",
  pages = "032"
}