@article{TournamentTCS,
  title = "Generalising submodularity and Horn clauses: tractable optimization problems defined by tournament pair multimorphisms",
  author = "David Cohen and Martin Cooper and Peter Jeavons",
  year = "2008",
  journal = "Theoretical Computer Science",
  number = "1-3",
  pages = "36-51",
  publisher = "Elsevier",
  volume = "401",
  doi = "doi:10.1016/j.tcs.2008.03.015",
}