@article{LiWu2004,
  author    = {{Li, Xiao Chun and Wu, Jia Bang}},
  title     = {{Study of periodic numbers in the $3N+1$ conjecture}},
  journal   = {{J. Huazhong Univ. Sci. Technol. Nat. Sci.}},
  year      = {{2004}},
  volume    = {{32}},
  number    = {{10}},
  pages     = {{100--101}},
  note      = {{MR 2121229}},
}