@misc{indiciae4faddbca9bad,
  title = {Exploration geophysics calculator programs for use on Hewlett-Packard models 67 and 97 programmable calculators},
  author = {David L. Campbell and Raymond D. Watts},
  year = {1978},
  doi = {10.3133/ofr78815},
  url = {https://pubs.usgs.gov/publication/ofr78815},
  note = {Source identifier: ofr78815}
}