@misc{indiciaee97ec48dc3d2,
  title = {The U.S. Geological Survey Modular Ground-Water Model - PCGN: A Preconditioned Conjugate Gradient Solver with Improved Nonlinear Control},
  author = {Richard L. Naff and Edward R. Banta},
  year = {2008},
  doi = {10.3133/ofr20081331},
  url = {https://pubs.usgs.gov/publication/ofr20081331},
  note = {Source identifier: ofr20081331}
}