@article{Hawking1966,
  author = {Hawking, Stephen William  and Bondi, Hermann },
  title = {The occurrence of singularities in cosmology},
  journal = {Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences},
  volume = {294},
  number = {1439},
  pages = {511-521},
  year = {1966},
  doi = {10.1098/rspa.1966.0221},
}
