@misc{indiciae09abc25c09c4,
  title = {Map showing geologic structure and altitude of the top of the Minnelusa Formation and orientation of mapped cave passages in the Madison Limestone, southern Black Hills, South Dakota},
  author = {K. D. Peter and K. R. Mills and C. L. Loskot},
  year = {1991},
  doi = {10.3133/wri864167},
  url = {https://pubs.usgs.gov/publication/wri864167},
  note = {Source identifier: wri864167}
}