@article{CTGDC_1982__23_4_407_0,
     author = {Mora, Ferdinando and Mora, Fulvio},
     title = {Quotients, fractions, symmetrizations},
     journal = {Cahiers de topologie et g\'eom\'etrie diff\'erentielle},
     pages = {407--424},
     publisher = {Dunod \'editeur, publi\'e avec le concours du CNRS},
     volume = {23},
     number = {4},
     year = {1982},
     mrnumber = {693507},
     zbl = {0514.18007},
     language = {en},
     url = {http://archive.numdam.org/item/CTGDC_1982__23_4_407_0/}
}