K
[KSW87] Johannes Köbler, Uwe Schöning, and Klaus W. Wagner. The difference and truth-table hierarchies for NP. RAIRO – Informatique Théorique et Applications 21(4):419-435. EDP Sciences, 1987. 
@article{rairo-ita21(4)-KSW,
  author =              {K{\"o}bler, Johannes and Sch{\"o}ning, Uwe and
                         Wagner, Klaus W.},
  title =               {The difference and truth-table hierarchies for~{NP}},
  publisher =           {EDP Sciences},
  journal =             {RAIRO~-- Informatique Th{\'e}orique et Applications},
  volume =              {21},
  number =              {4},
  pages =               {419-435},
  year =                {1987},
}
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