@article{JIS_2003__6_4_a6,
     author = {Christophe, Julie and Doignon, Jean-Paul and Fiorini, Samuel},
     title = {Counting biorders},
     journal = {Journal of integer sequences},
     publisher = {mathdoc},
     volume = {6},
     number = {4},
     year = {2003},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JIS_2003__6_4_a6/}
}