@misc{indiciae2363ac675a7f,
  title = {Four preliminary aeromagnetic maps covering Clay, Knox, Sullivan, and Vigo Counties, Indiana},
  author = {John R. Henderson},
  year = {1949},
  doi = {10.3133/ofr4929},
  url = {https://pubs.usgs.gov/publication/ofr4929},
  note = {Source identifier: ofr4929}
}