@article{MAN_1961__143_160854,
     author = {R.C. READ},
     title = {A note on the number of functional digraphs.},
     journal = {Mathematische Annalen},
     pages = {109--110},
     publisher = {mathdoc},
     volume = {143},
     year = {1961},
     zbl = {0096.38201},
     url = {http://geodesic.mathdoc.fr/item/MAN_1961__143_160854/}
}