@misc{indiciae2d31f2742296,
  title = {Slope measurement from contour maps},
  author = {Lee, Y. H. and Parks, C. M. and Scheps, B. B.},
  year = {1970},
  url = {https://ntrs.nasa.gov/citations/19700019413},
  note = {Source identifier: 19700019413}
}