@article{kleinman1982,
  title={Efficacious Form for Model Pseudopotentials},
  author={Leonard Kleinman and D. M. Bylander},
  year={1982},
  journal={Physical Review Letters},
  doi={10.1103/physrevlett.48.1425},
  url={https://doi.org/10.1103/physrevlett.48.1425}
}