K
[Kar78] Richard M. Karp. A characterization of the minimum cycle mean in a digraph. Discrete Mathematics 23(3):309-311. Elsevier, September 1978. 
@article{dm23(3)-Kar,
  author =              {Karp, Richard M.},
  title =               {A~characterization of the minimum cycle mean in a
                         digraph},
  publisher =           {Elsevier},
  journal =             {Discrete Mathematics},
  volume =              {23},
  number =              {3},
  pages =               {309-311},
  year =                {1978},
  month =               sep,
}
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