@article{10_1090_S0894_0347_1990_1065053_0,
     author = {Alon, Noga and Seymour, Paul and Thomas, Robin},
     title = {A separator theorem for nonplanar graphs},
     journal = {Journal of the American Mathematical Society},
     pages = {801--808},
     year = {1990},
     volume = {03},
     number = {4},
     doi = {10.1090/S0894-0347-1990-1065053-0},
     url = {http://geodesic.mathdoc.fr/articles/10.1090/S0894-0347-1990-1065053-0/}
}