@article{10_37236_1803,
     author = {Paulette Lieby},
     title = {Antichains on three levels},
     journal = {The electronic journal of combinatorics},
     year = {2004},
     volume = {11},
     number = {1},
     doi = {10.37236/1803},
     zbl = {1055.05148},
     url = {http://geodesic.mathdoc.fr/articles/10.37236/1803/}
}