@misc{indiciae3082c20cd613,
  title = {Detection of underground voids in Ohio by use of geophysical methods},
  author = {Jens Munk and R. A. Sheets},
  year = {1997},
  doi = {10.3133/wri974221},
  url = {https://pubs.usgs.gov/publication/wri974221},
  note = {Source identifier: wri974221}
}