@misc{indiciaed87feee19548,
  title = {The optimal sun angle for obtaining photographs of Martian surface features from orbit},
  author = {Joseph M. Boyce and Arthur L. Dial and Harold Masursky},
  year = {1976},
  doi = {10.3133/ofr76624},
  url = {https://pubs.usgs.gov/publication/ofr76624},
  note = {Source identifier: ofr76624}
}