@article{M2AN_1987__21_1_27_0,
     author = {El Hatri, Mohamed},
     title = {Estimation d'erreur optimale et de type superconvergence de la m\'ethode des \'el\'ements finis pour un probl\`eme aux limites, d\'eg\'en\'er\'e},
     journal = {ESAIM: Mod\'elisation math\'ematique et analyse num\'erique},
     pages = {27--61},
     publisher = {AFCET - Gauthier-Villars},
     address = {Paris},
     volume = {21},
     number = {1},
     year = {1987},
     mrnumber = {882686},
     zbl = {0646.65077},
     language = {fr},
     url = {http://archive.numdam.org/item/M2AN_1987__21_1_27_0/}
}