@article{Barmpalias2011ChaitinSHalting,
  year      = 2011,
  publisher = {R. Soc.},
  volume    = {467},
  number    = {2134},
  pages     = {2912--2926},
  author    = {G. Barmpalias and A. E. M. Lewis},
  title     = {Chaitin's halting probability and the compression of strings using oracles},
  journal   = {Proc. R. Soc. A},
}