  The role of the small-norm amplitudes in extended RPA theories such as the
particle-particle and hole-hole components of one-body amplitudes and the
two-body amplitudes other than two particle - two holes components are
investigated for the one-dimensional Hubbard model using an extended RPA
derived from the time-dependent density-matrix theory. It is found that these
amplitudes cannot be neglected in strongly interacting regions where the
effects of ground-state correlations are significant.
