@misc{indiciae617ebd2d0d92,
  title = {Contour surveying system Patent},
  author = {Batts, C. N. and Gibson, F. W. and Hess, R. W.},
  year = {1970},
  url = {https://ntrs.nasa.gov/citations/19710008111},
  note = {Source identifier: 19710008111}
}