@incollection{Barmpalias2006ImmunityPropertiesN,
  year      = 2006,
  publisher = {Springer},
  pages     = {694--703},
  author    = {B. Afshari and G. Barmpalias and S. B. Cooper},
  title     = {Immunity Properties and the n-C.E. Hierarchy},
  booktitle = {Lect. Notes Comput. Sci.},
}