@article{Urata1999,
  author    = {{Toshio Urata}},
  title     = {{Collatz Problem IV}},
  journal   = {{Epsilon (The Bulletin of the Society of Mathematics Education of Aichi Univ. of Education) [Aichi Kyoiku Daigaku Sugaku Kyoiku Gakkai shi]}},
  year      = {{1999}},
  volume    = {{41}},
  pages     = {{111-116}},
}