@article{Crandall1978,
  author    = {{Richard E. Crandall}},
  title     = {{On the ``$3x + 1$'' problem}},
  journal   = {{Math. Comp.}},
  year      = {{1978}},
  volume    = {{32}},
  pages     = {{1281--1292}},
  note      = {{MR 58 #494}},
}