@misc{mse-1,
  title = {Combinatorial Proof of falling factorial and binomial theorem},
  author = {ajotatxe},
  howpublished = {Mathematics Stack Exchange},
  note = {\url{https://math.stackexchange.com/q/1271700} (version: 2015-05-07),
      author profile: \url{https://math.stackexchange.com/users/132456/ajotatxe}}
}

@misc{mse-2,
  title = {Combinatorial Proof of falling factorial and binomial theorem},
  author = {grapher},
  howpublished = {Mathematics Stack Exchange},
  note = {\url{https://math.stackexchange.com/q/1271688} (version: 2016-08-27),
      author profile: \url{https://math.stackexchange.com/users/199155/grapher}}
}

@misc{mse-3,
  title = {Combinatorial Proof of falling factorial and binomial theorem},
  author = {Foobaz John},
  howpublished = {Mathematics Stack Exchange},
  note = {\url{https://math.stackexchange.com/q/2161558} (version: 2017-11-14),
     author profile: \url{https://math.stackexchange.com/users/302692/foobaz-john}}
}

@misc{mse-4,
  title = {Combinatorial Proof of falling factorial and binomial theorem},
  author = {Brian M. Scott},
  howpublished = {Mathematics Stack Exchange},
  note = {\url{https://math.stackexchange.com/q/1271983} (version: 2015-05-07),
      author profile: \url{https://math.stackexchange.com/users/12042/brian-m-scott}},
}