@article{CTGDC_1991__32_3_191_0,
     author = {Janelidze, George},
     title = {What is a double central extension ? (the question was asked by {Ronald} {Brown)}},
     journal = {Cahiers de Topologie et G\'eom\'etrie Diff\'erentielle Cat\'egoriques},
     pages = {191--201},
     publisher = {Dunod \'editeur, publi\'e avec le concours du CNRS},
     volume = {32},
     number = {3},
     year = {1991},
     mrnumber = {1158108},
     zbl = {0762.18003},
     language = {en},
     url = {http://archive.numdam.org/item/CTGDC_1991__32_3_191_0/}
}