@article{sheffieldlittle2012,
  title={Little change in global drought over the past 60 years},
  author={Justin Sheffield and Eric F. Wood and Michael L. Roderick},
  journal={Nature},
  volume={491},
  number={7424},
  pages={435-438},
  year={2012},
  doi={10.1038/nature11575},
  url={http://dx.doi.org/10.1038/nature11575}
}