@article{PDML_1987___1B_1_0,
     author = {Lichnerowicz, Andr\'e},
     title = {Extensions essentielles d'alg\`ebres de {Lie} classiques de dimensions infinies},
     journal = {Publications du D\'epartement de math\'ematiques (Lyon)},
     pages = {1--16},
     publisher = {Universit\'e Claude Bernard - Lyon 1},
     number = {1B},
     year = {1987},
     mrnumber = {907063},
     zbl = {0598.17009},
     language = {fr},
     url = {http://www.numdam.org/item/PDML_1987___1B_1_0/}
}