@misc{indiciae77500029fe4d,
  title = {Efficient implementations of the Polak-Ribiere conjugate gradient algorithm.},
  author = {Klessig, R. and Polak, E.},
  year = {1972},
  url = {https://ntrs.nasa.gov/citations/19720058265},
  note = {Source identifier: 19720058265}
}