@article{BSMF_1970__98__337_0,
     author = {Gr\"abe, P.J. and Viljoen, G.},
     title = {Characterizations of classes of left {Ext-reproduced} groups},
     journal = {Bulletin de la Soci\'et\'e Math\'ematique de France},
     pages = {337--358},
     publisher = {Soci\'et\'e math\'ematique de France},
     volume = {98},
     year = {1970},
     doi = {10.24033/bsmf.1707},
     zbl = {0188.06601},
     language = {en},
     url = {http://www.numdam.org/articles/10.24033/bsmf.1707/}
}