@incollection{AST_1975__24-25__37_0,
     author = {Gras, Georges},
     title = {Parit\'e du nombre de classes et unit\'es cyclotomiques},
     booktitle = {Journ\'ees arithm\'etiques de Bordeaux},
     series = {Ast\'erisque},
     pages = {37--45},
     publisher = {Soci\'et\'e math\'ematique de France},
     number = {24-25},
     year = {1975},
     mrnumber = {382224},
     zbl = {0312.12014},
     language = {fr},
     url = {http://www.numdam.org/item/AST_1975__24-25__37_0/}
}