@article{Zarnowski2008,
  author    = {{Zarnowski, Roger E.}},
  title     = {{The congruence structure of the $3x+1$ map}},
  journal   = {{Fibonacci Quarterly}},
  year      = {{2008}},
  volume    = {{46/47}},
  number    = {{2}},
  pages     = {{115--125}},
  note      = {{MR 2010c:11037}},
}