@article{Coppersmith1975,
  author    = {{Don Coppersmith}},
  title     = {{The complement of certain recursively defined sets}},
  journal   = {{J. Combinatorial Theory, Series A}},
  year      = {{1975}},
  volume    = {{18}},
  number    = {{3}},
  pages     = {{243--251}},
  note      = {{MR 51 $\#$5477}},
}