Filtration Patterns for Representations of Algebraic Groups and Their Frobenius Kernels. Steven R. Doty, John B. Sullivan (1987) Mathematische Zeitschrift
Filtrations of cohomology modules for Chevalley groups Henning Haahr Andersen (1983) Annales scientifiques de l'École Normale Supérieure
Filtrations of the modules for Chevalley groups arising from admissible lattices. Zongzhu Lin (1992) Mathematische Zeitschrift
Functions on the universal cover of the prinicpal nilpotent orbit. William A. Graham (1992) Inventiones mathematicae