@article{CTGDC_1981__22_4_399_0,
     author = {Porst, Hans-E.},
     title = {Characterization of injective envelopes},
     journal = {Cahiers de topologie et g\'eom\'etrie diff\'erentielle},
     pages = {399--406},
     publisher = {Dunod \'editeur, publi\'e avec le concours du CNRS},
     volume = {22},
     number = {4},
     year = {1981},
     mrnumber = {639050},
     zbl = {0473.18010},
     language = {en},
     url = {http://www.numdam.org/item/CTGDC_1981__22_4_399_0/}
}