@article{PDML_1967__4_2_A2_0,
     author = {Ravel, J.},
     title = {Injectivit\'e ; g\'en\'eralisations et applications {Extensions} essentielles dans un treillis de {Johnson}},
     journal = {Publications du D\'epartement de math\'ematiques (Lyon)},
     pages = {1--73},
     publisher = {Universit\'e Claude Bernard - Lyon 1},
     volume = {4},
     number = {2},
     year = {1967},
     mrnumber = {221990},
     zbl = {0154.28101},
     language = {fr},
     url = {http://www.numdam.org/item/PDML_1967__4_2_A2_0/}
}