@article{Barmpalias2011UpperBoundsIdeals,
  year      = 2011,
  publisher = {Elsevier},
  volume    = {162},
  number    = {6},
  pages     = {465--473},
  author    = {G. Barmpalias and A. Nies},
  title     = {Upper bounds on ideals in the computably enumerable Turing degrees},
  journal   = {Ann. Pure Appl. Logic},
}