S
[Sav70] Walter Savitch. Relationships between nondeterministic and deterministic tape complexities. Journal of Computer and System Sciences 4(2):177-192. Academic Press, April 1970. 
@article{jcss4(2)-Sav,
  author =              {Savitch, Walter},
  title =               {Relationships between nondeterministic and
                         deterministic tape complexities},
  publisher =           {Academic Press},
  journal =             {Journal of Computer and System Sciences},
  volume =              {4},
  number =              {2},
  pages =               {177-192},
  year =                {1970},
  month =               apr,
  doi =                 {10.1016/S0022-0000(70)80006-X},
}
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