@article{JAC_1999__9_2_a2,
     author = {Ruelle, David},
     title = {Counting unbranched subgraphs},
     journal = {Journal of Algebraic Combinatorics},
     pages = {157--160},
     publisher = {mathdoc},
     volume = {9},
     number = {2},
     year = {1999},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JAC_1999__9_2_a2/}
}