  We introduce a method that allows the evaluation of general expressions for
the spectral functions of the one-dimensional Hubbard model for all values of
the on-site electronic repulsion U. The spectral weights are expressed in terms
of pseudofermion operators such that the spectral functions can be written as a
convolution of pseudofermion dynamical correlation functions. Our results are
valid for all finite energy and momentum values and are used elsewhere in the
study of the unusual finite-energy properties of quasi-one-dimensional
compounds and the new quantum systems of ultra-cold fermionic atoms on an
optical lattice.
