@article{JIS_2005__8_2_a6,
     author = {Brinkmann,  Gunnar and McKay,  Brendan D.},
     title = {Counting unlabelled topologies and transitive relations},
     journal = {Journal of integer sequences},
     year = {2005},
     volume = {8},
     number = {2},
     zbl = {1064.05068},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JIS_2005__8_2_a6/}
}