@article{10_37236_610,
     author = {Leonard J. Schulman},
     title = {The quantifier semigroup for bipartite graphs},
     journal = {The electronic journal of combinatorics},
     year = {2011},
     volume = {18},
     number = {1},
     doi = {10.37236/610},
     zbl = {1232.06018},
     url = {http://geodesic.mathdoc.fr/articles/10.37236/610/}
}