@misc{indiciae99ea3f99fe73,
  title = {Indiana coal and associated rock samples collected from 1975 to 1977},
  author = {C.L. Oman and W.A. Hassenmueller and L. J. Bragg},
  year = {1992},
  doi = {10.3133/ofr92682},
  url = {https://pubs.usgs.gov/publication/ofr92682},
  note = {Source identifier: ofr92682}
}