@article{SLC_2004-2005_51_a6,
     author = {Mark Dukes},
     title = {On the {Number} of {Matroids} of a {Finite} {Set}},
     journal = {S\'eminaire lotharingien de combinatoire},
     publisher = {mathdoc},
     volume = {51},
     year = {2004-2005},
     url = {http://geodesic.mathdoc.fr/item/SLC_2004-2005_51_a6/}
}