@misc{indiciae01407aa37d91,
  title = {Analytical results of insoluble-residue samples from the Paducah 1 degree by 2 degrees Quadrangle, Missouri, Illinois, and Kentucky; drill hole Nos. K1-K4},
  author = {John H. Bullock and Helen W. Folger and John D. Sharkey and Cliff D. Taylor},
  year = {1991},
  doi = {10.3133/ofr91372b},
  url = {https://pubs.usgs.gov/publication/ofr91372B},
  note = {Source identifier: ofr91372B}
}