  With the eigen-functional bosonization method, we study one-dimensional
strongly correlated electron systems with large momentum ($2k_{F}$ and/or
$4k_{F}$) transfer term(s), and demonstrate that this kind of problems ends in
to solve the Eikonal-type equations, and these equations are universal, and
independent of whether or not the system is integrable. In contrast to usual
perturbation theory, this method is valid not only for weak electron
interaction, but also for strong electron interaction. Comparing with exact
solution of some integrable models, it can give correct results in one-loop
approximation. This method can also be used to study electron-phonon
interaction systems, and two coupled spin chain or quantum wire systems.
