@manual{Ye1989,
  title={SOLNP USERS'GUIDE},
  author={Ye, Yinyu},
  year={1989}
}

@article{Hock1980,
  title={Test examples for nonlinear programming codes},
  author={Hock, W and Schittkowski, K},
  journal={Journal of Optimization Theory and Applications},
  volume={30},
  number={1},
  pages={127--129},
  year={1980}
}

@article{Schittkowski2012,
  title={More test examples for nonlinear programming codes},
  author={Schittkowski, Klaus},
  journal={Lecture Notes in Economics and Mathematical Systems},
  volume={282},
  year={2012},
}
