@article{SF_1971__3_133871,
     author = {D. Zupnik},
     title = {Cayley functions.},
     journal = {Semigroup forum},
     pages = {349--358},
     publisher = {mathdoc},
     volume = {3},
     year = {1971},
     zbl = {0244.20069},
     url = {http://geodesic.mathdoc.fr/item/SF_1971__3_133871/}
}