First appeared in passing in the basic paper of O.
We define a partial order on the set No,c of pairs (O,C), where O is a nilpotent orbit and C is a conjugacy class in A(O), Lusztig's canonical quotient of A(O).
Real and Rational Forms of Certain O2(?)-actions, and a Solution to the Weak Complexification Problem
The Combinatorics of Category O over symmetrizable Kac-Moody Algebras
We show that the structure of a block outside the critical hyperplanes of category O over a symmetrizable Kac-Moody algebra depends only on the corresponding integral Weyl group and its action on the parameters of the Verma modules.