@misc{indiciae1e372ba5d971,
  title = {Use of 35-mm color aerial photography to acquire mallard sex ratio data},
  author = {Edgar L. Ferguson and Dennis G. Jorde and John L. Sease},
  year = {1981},
  url = {https://pubs.usgs.gov/publication/1001697},
  note = {Source identifier: 1001697}
}