@article{SHC_1949-1950__2__A1_0,
     author = {Serre, J-P.},
     title = {Extension des applications - homotopie},
     journal = {S\'eminaire Henri Cartan},
     note = {talk:1},
     pages = {1--6},
     publisher = {Secr\'etariat math\'ematique},
     volume = {2},
     year = {1949-1950},
     language = {fr},
     url = {http://www.numdam.org/item/SHC_1949-1950__2__A1_0/}
}