@article{DMGT_1996_16_2_a9,
     author = {Richter, R.},
     title = {Observations on maps and \ensuremath{\delta}-matroids},
     journal = {Discussiones Mathematicae. Graph Theory},
     pages = {197--205},
     publisher = {mathdoc},
     volume = {16},
     number = {2},
     year = {1996},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/DMGT_1996_16_2_a9/}
}