@misc{indiciae88a05708479a,
  title = {A pointable, helicopter-based remote sensing data acquisition system for collecting bidirectional reflectance data},
  author = {Williams, Darrel L. and Walthall, Charles L. and Young, Douglas},
  year = {1991},
  url = {https://ntrs.nasa.gov/citations/19910016177},
  note = {Source identifier: 19910016177}
}