@article{SLC_1984_10_a13,
     author = {Wolfgang Degen and Klaus Leeb and Giuseppe Pirillo and Helmut Sperber},
     title = {Some {Things} {Some} {Functions} {May} {Be,} {Some} {Others} {Can't} {Be}},
     journal = {S\'eminaire lotharingien de combinatoire},
     publisher = {mathdoc},
     volume = {10},
     year = {1984},
     url = {http://geodesic.mathdoc.fr/item/SLC_1984_10_a13/}
}