@misc{indiciaee62fae9eb0cf,
  title = {Measuring coal thickness},
  author = {Barker, C. and Blaine, J. and Geller, G. and Robinson, R. and Summers, D. and Tyler, J.},
  year = {1980},
  url = {https://ntrs.nasa.gov/citations/19790000363},
  note = {Source identifier: 19790000363}
}