@misc{indiciae5e4429dd1289,
  title = {Preliminary geologic map of the Roberts Mountain quadrangle, Lewis and Clark County, Montana},
  author = {R. G. Schmidt and C.P. Strong},
  year = {1968},
  doi = {10.3133/i564},
  url = {https://pubs.usgs.gov/publication/i564},
  note = {Source identifier: i564}
}