@article{MOMA_1968__72_177416,
     author = {W.J. Schneider},
     title = {An {Elementary} {Proof} of a {Theorem} of {MacLane.}},
     journal = {Monatshefte f\"ur Mathematik},
     pages = {144--146},
     publisher = {mathdoc},
     volume = {72},
     year = {1968},
     zbl = {0165.40202},
     url = {http://geodesic.mathdoc.fr/item/MOMA_1968__72_177416/}
}