@misc{indiciaee0c35d898718,
  title = {Preliminary map of diatremes and alkalic ultramafic intrusions in the Missouri River Breaks and vicinity, north-central Montana},
  author = {B. C. Hearn},
  year = {1979},
  doi = {10.3133/ofr791128},
  url = {https://pubs.usgs.gov/publication/ofr791128},
  note = {Source identifier: ofr791128}
}