@article{SF_1971__3_133843,
     author = {M.S. Putcha},
     title = {Commutative semigroups whose homomorphic images in groups are groups.},
     journal = {Semigroup forum},
     pages = {51--57},
     publisher = {mathdoc},
     volume = {3},
     year = {1971},
     zbl = {0235.20058},
     url = {http://geodesic.mathdoc.fr/item/SF_1971__3_133843/}
}