@incollection{Akin2004,
  author    = {{Ethan Akin}},
  title     = {{Why is the $3x+1$ Problem Hard?}},
  booktitle = {{Chapel Hill Ergodic Theory Workshops}},
  publisher = {{Amer. Math. Soc.}},
  year      = {{2004}},
  volume    = {{356}},
  pages     = {{1--20}},
  note      = {{MR 2005f:37031}},
}