@article{MZ_1961__75_169898,
     author = {Richard Friedberg},
     title = {The uniqueness of finite division for recursive equivalence types.},
     journal = {Mathematische Zeitschrift},
     pages = {3--7},
     year = {1961},
     volume = {75},
     zbl = {0093.01203},
     url = {http://geodesic.mathdoc.fr/item/MZ_1961__75_169898/}
}