@article{Barmpalias2008Pi01,
  title   = {?<inf>1</inf><sup>0</sup> classes, L R degrees and Turing degrees},
  journal = {Ann. Pure Appl. Logic},
  year    = {2008},
  volume  = {156},
  number  = {1},
  pages   = {21-38},
  author  = {G. Barmpalias and A. E. M. Lewis and F. Stephan},
}