@article{Filipponi1991,
  author    = {{Piero Filipponi}},
  title     = {{On the $3n+1$ Problem: Something Old, Something New}},
  journal   = {{Rendiconti di Mathematica, Serie VII, Roma}},
  year      = {{1991}},
  volume    = {{11}},
  pages     = {{85--103}},
  note      = {{MR 92i:11031}},
}