@article{BergMeinardus1994,
  author    = {{Lothar Berg and Günter Meinardus}},
  title     = {{Functional equations connected with the Collatz problem}},
  journal   = {{Results in Math.}},
  year      = {{1994}},
  volume    = {{25}},
  pages     = {{1--12}},
  note      = {{MR 95d:11025}},
}