@article{JAC_2007__25_4_a4,
     author = {Westbury, Bruce W.},
     title = {Enumeration of non-positive planar trivalent graphs},
     journal = {Journal of Algebraic Combinatorics},
     pages = {357--373},
     publisher = {mathdoc},
     volume = {25},
     number = {4},
     year = {2007},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JAC_2007__25_4_a4/}
}