@incollection{AST_1983__101-102__208_0,
     author = {Lusztig, George},
     title = {Singularities, character formulas, and a $q$-analog of weight multiplicities},
     booktitle = {Analyse et topologie sur les espaces singuliers (II-III) - 6 - 10 juillet 1981},
     series = {Ast\'erisque},
     pages = {208--229},
     publisher = {Soci\'et\'e math\'ematique de France},
     number = {101-102},
     year = {1983},
     zbl = {0561.22013},
     mrnumber = {737932},
     language = {en},
     url = {http://www.numdam.org/item/AST_1983__101-102__208_0/}
}