@article{10_37236_1867,
     author = {Herbert S. Wilf},
     title = {The {Redheffer} matrix of a partially ordered set},
     journal = {The electronic journal of combinatorics},
     year = {2004},
     volume = {11},
     number = {2},
     doi = {10.37236/1867},
     zbl = {1077.15009},
     url = {http://geodesic.mathdoc.fr/articles/10.37236/1867/}
}