@article{KlarnerRado1974,
  author    = {{David A. Klarner and Richard Rado}},
  title     = {{Arithmetic properties of certain recursively defined sets}},
  journal   = {{Pacific J. Math.}},
  year      = {{1974}},
  volume    = {{53}},
  pages     = {{445--463}},
  note      = {{MR 50  $\#$9784}},
}