@misc{indiciae675335651e80,
  title = {Coal-shale interface detection system},
  author = {Campbell, R. A. and Hudgins, J. L. and Morris, P. W. and Reid, H., Jr. and Zimmerman, J. E.},
  year = {1979},
  url = {https://ntrs.nasa.gov/citations/19800006166},
  note = {Source identifier: 19800006166}
}