@article{PMIHES_1978__48__39_0,
     author = {Lawrence Breen},
     title = {Extensions du groupe additif},
     journal = {Publications Math\'ematiques de l'IH\'ES},
     pages = {39--125},
     year = {1978},
     publisher = {Institut des Hautes \'Etudes Scientifiques},
     volume = {48},
     doi = {10.1007/BF02684313},
     mrnumber = {516914},
     zbl = {0404.14018},
     language = {fr},
     url = {https://pmihes.centre-mersenne.org/articles/10.1007/BF02684313/}
}