@misc{indiciaea17cdd64722a,
  title = {Age determination of mallards},
  author = {Gary L. Krapu and Douglas H. Johnson and C.W. Dane},
  year = {1979},
  doi = {10.2307/3800347},
  url = {https://pubs.usgs.gov/publication/1001538},
  note = {Source identifier: 1001538}
}