This bears upon the construction of non-trivial residual square-integrable automorphic forms coming from cuspforms on smaller groups, anticipating that such automorphic forms occur as residues of Eisenstein series. For example, we can see why there is no interesting (i.e., non-constant) non-cuspidal discrete spectrum for GL(2) nor for GL(3), but only for GL(4) and larger groups. Namely, the Eis...