@article{SF_1995__50_3_135390,
     author = {P.A. Grillet},
     title = {The number of commutative semigroups of order {N.}},
     journal = {Semigroup forum},
     pages = {317--326},
     publisher = {mathdoc},
     volume = {50},
     number = {3},
     year = {1995},
     zbl = {0831.20079},
     url = {http://geodesic.mathdoc.fr/item/SF_1995__50_3_135390/}
}