@article{SE_1957-1958__1__A5_0,
     author = {de Cahvalho, Carlos A. A.},
     title = {Sur les deuxi\`emes obstructions},
     journal = {S\'eminaire de topologie et g\'eom\'etrie diff\'erentielle},
     note = {talk:13},
     pages = {1--13},
     publisher = {Secr\'etariat math\'ematique},
     volume = {1},
     year = {1957-1958},
     zbl = {0158.42003},
     language = {fr},
     url = {http://www.numdam.org/item/SE_1957-1958__1__A5_0/}
}