@article{Barmpalias2003ApproximationStructureComputably,
  year      = 2003,
  publisher = {Cambridge Univ. Press},
  volume    = {68},
  number    = {03},
  pages     = {885--922},
  author    = {G. Barmpalias},
  title     = {The approximation structure of a computably approximable real },
  journal   = {J. Symb. Log.},
}