||Consider a pair (G, G') where G is a connected reductive group over a
local field and G' be a subgroup containing the derived subgroup of G.
A seemingly simple problem is to investigate the branching of an
admissible representation of G restricted to G'. The most well-known
case is (G, G') = (GL(n), SL(n)), which yields the Langlands'
correspondence for SL(n). This approach has been generalized recently
to all inner forms by Hiraga and Saito. In this talk, I will try to
introduce the basic ideas and related issues.