@misc{indiciae77ee55cbc1e1,
  title = {Variability of Mars' North Polar water ice cap: I. Analysis of Mariner 9 and Viking Orbiter imaging data},
  author = {Deborah S. Bass and Kenneth E. Herkenhoff and David A. Paige},
  year = {2000},
  doi = {10.1006/icar.1999.6300},
  url = {https://pubs.usgs.gov/publication/70022940},
  note = {Source identifier: 70022940}
}