@article{10_37236_2534,
     author = {Evan Morgan and Bogdan Oporowski},
     title = {Bounding tree-width via contraction on the projective plane and torus},
     journal = {The electronic journal of combinatorics},
     year = {2015},
     volume = {22},
     number = {4},
     doi = {10.37236/2534},
     zbl = {1323.05042},
     url = {http://geodesic.mathdoc.fr/articles/10.37236/2534/}
}