@misc{indiciaedc1319634ae8,
  title = {Concentrations of N 2 , O 2 , CO 2 , and He in soil gases collected in the northern San Luis Valley, Colorado},
  author = {M. E. Hinkle},
  year = {1993},
  doi = {10.3133/ofr93584},
  url = {https://pubs.usgs.gov/publication/ofr93584},
  note = {Source identifier: ofr93584}
}