@article{Barmpalias2006HypersimpleFreeC,
  year      = 2006,
  publisher = {Duke Univ. Press},
  volume    = {47},
  number    = {3},
  pages     = {361--370},
  author    = {G. Barmpalias and A. E. M. Lewis},
  title     = {The Hypersimple-Free C.E. {WTT} Degrees Are Dense in the C.E. {WTT} Degrees},
  journal   = {Notre Dame J. Form. Log.},
}