Measuring pain intensity in headache trials: which scale to use?

@article{Loder2012MeasuringPI,
  title={Measuring pain intensity in headache trials: which scale to use?},
  author={Elizabeth Loder and Rebecca Burch},
  journal={Cephalalgia : an international journal of headache},
  year={2012},
  volume={32 3},
  pages={179-82}
}