@article{10_37236_80,
     author = {L\'aszl\'o Lov\'asz and Alexander Schrijver},
     title = {Semidefinite functions on categories},
     journal = {The electronic journal of combinatorics},
     year = {2009},
     volume = {16},
     number = {2},
     doi = {10.37236/80},
     zbl = {1226.05163},
     url = {http://geodesic.mathdoc.fr/articles/10.37236/80/}
}