@article{MZ_1972__128_171794,
     author = {Urs Stammbach},
     title = {Varietal {Homology} and {Parafree} {Groups.}},
     journal = {Mathematische Zeitschrift},
     pages = {153--168},
     publisher = {mathdoc},
     volume = {128},
     year = {1972},
     zbl = {0253.20076},
     url = {http://geodesic.mathdoc.fr/item/MZ_1972__128_171794/}
}