I
[Imm88] Neil Immerman. Nondeterministic Space is Closed Under Complementation. SIAM Journal on Computing 17(5):935-938. Society for Industrial and Applied Math., October 1988. 
@article{siamcomp17(5)-Imm,
  author =              {Immerman, Neil},
  title =               {Nondeterministic Space is Closed Under
                         Complementation},
  publisher =           {Society for Industrial and Applied Math.},
  journal =             {SIAM Journal on Computing},
  volume =              {17},
  number =              {5},
  pages =               {935-938},
  year =                {1988},
  month =               oct,
}
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