@article{charnes1978,
  title={Measuring the efficiency of decision making units},
  author={A. Charnes and W. W. Cooper and Edwardo L. Rhodes},
  year={1978},
  journal={European Journal of Operational Research},
  doi={10.1016/0377-2217(78)90138-8},
  url={https://doi.org/10.1016/0377-2217(78)90138-8}
}