EXTENSIONS OF SIMPLE MODULES FOR SPECIAL ALGEBRAIC-GROUPS

We compute the groups Ext(G)l(L, M) for any two simple rational module s for the simple algebraic groups G of type C2 and F4 in characteristi c 2 and type G2 in characteristic 3 by exploiting the special endomorp hisms which exist for these groups. (C) 1994 Academic Press, Inc.