@misc{indiciaeb222274df2a9,
  title = {Preliminary seismotectonic map of the central Mississippi Valley and environs},
  author = {A. V. Heyl and F. A. McKeown},
  year = {1978},
  doi = {10.3133/mf1011},
  url = {https://pubs.usgs.gov/publication/mf1011},
  note = {Source identifier: mf1011}
}