@misc{indiciae2751e3ade22d,
  title = {Early Tertiary age of pitchstone in the northern Black Hills, South Dakota},
  author = {J. A. Redden and J. D. Obradovich and C. W. Naeser and R. E. Zartman and J.J. Norton},
  year = {1983},
  doi = {10.1126/science.220.4602.1153},
  url = {https://pubs.usgs.gov/publication/70011208},
  note = {Source identifier: 70011208}
}