@article{O'Loughlin:20096+,
  author = "O'Loughlin, Martin",
  title = "{Penrose Limits, Singularities and DLCQ}",
  doi = "10.22323/1.075.0023",
  journal = "PoS",
  year = 2009,
  volume = "BHs, GR and Strings",
  pages = "023"
}