@article{Venturini1989,
  author    = {{Giovanni Venturini}},
  title     = {{On the $3x + 1$ Problem}},
  journal   = {{Adv. Appl. Math}},
  year      = {{1989}},
  volume    = {{10}},
  pages     = {{344--347}},
  note      = {{MR 90i:11020}},
}