Frank H. Mathis. A Generalized Birthday Problem. SIAM Review, 33(2):265-270, 1991. [doi]
@article{Mathis91-0,
  title = {A Generalized Birthday Problem},
  author = {Frank H. Mathis},
  year = {1991},
  doi = {10.1137/1033051},
  url = {http://dx.doi.org/10.1137/1033051},
  researchr = {https://researchr.org/publication/Mathis91-0},
  cites = {0},
  citedby = {0},
  journal = {SIAM Review},
  volume = {33},
  number = {2},
  pages = {265-270},
}