@misc{indiciaeb724439a814c,
  title = {An interactive program to display user-generated or file-based maps on a personal computer monitor},
  author = {W. H. Langer and R.W. Stephens},
  year = {1987},
  doi = {10.3133/ofr87676},
  url = {https://pubs.usgs.gov/publication/ofr87676},
  note = {Source identifier: ofr87676}
}