@article{Wirsching2000,
  author    = {{Günther J. Wirsching}},
  title     = {{Über das $3n + 1$ Problem}},
  journal   = {{Elem. Math.}},
  year      = {{2000}},
  volume    = {{55}},
  pages     = {{142--155}},
  note      = {{MR 2002h:11022}},
}