@article{Collatz1986,
  author    = {{Lothar Collatz}},
  title     = {{On the Motivation and Origin of the $(3n +  1)$-Problem}},
  journal   = {{J. of Qufu Normal University, Natural Science Edition [Qufu shi fan da xue xue bao. Zi ran ke xue ban]}},
  year      = {{1986}},
  volume    = {{12}},
  number    = {{3}},
  pages     = {{9--11}},
  note      = {{Chinese, transcribed by Zhi-Ping Ren}},
}