@misc{indiciae2230ecde3947,
  title = {Self-recording portable soil penetrometer},
  author = {Costes, N. C. and Sturm, R. G. and Norton, R. H. and Campbell, G. E.},
  year = {1973},
  url = {https://ntrs.nasa.gov/citations/19730010693},
  note = {Source identifier: 19730010693}
}