@article{Callan03,
  title = {Problem 11013},
  author = {David Callan},
  year = {2003},
  url = {http://www.jstor.org/stable/3647833},
  researchr = {https://researchr.org/publication/Callan03},
  cites = {0},
  citedby = {0},
  journal = {The American Mathematical Monthly},
  volume = {110},
  number = {5},
  pages = {438},
}