  Several kinds of spin density wave (SDW) states with both quarter-filled band
and dimerization are reexamined for a one-dimensional system with on-site,
nearest-neighbor and next-nearest-neighbor repulsive interactions, which has
been investigated by Kobayashi et al. (J. Phys. Soc. Jpn. 67 (1998) 1098).
Within the mean-field theory, the ground state and the response to the density
variation are calculated in terms of phase variables, $\theta$ and $\phi$,
where $\theta$ expresses the charge fluctuation of SDW and $\phi$ describes the
relative motion between density wave with up spin and that with down spin
respectively. It is shown that the exotic state of coexistence of 2k_F-SDW and
2k_F-charge density wave (CDW) is followed by 4k_F-SDW but not by 4k_F-CDW
where k_F denotes a Fermi wave vector. The harmonic potential with respect to
the variation of $\theta$ and/or $\phi$ disappears for the interactions, which
lead to the boundary between the pure 2k_F-SDW state and the corresponding
coexistent state.
