2.    S. M. Bhattacharjee ans S. Mukherji             J. Phys. A 31, L695 (1998).
         Title: Incommensuration in quantum antiferromagnetic chain
         cond-mat/9808219  pdf

1.    S. M. Bhattacharjee, T. Nattermann and C. Ronnewinkel Phys.Rev. B 58, 2658 (1998).
         Title:      Incommensurate phase of the pure and doped spin-Peierls system CuGeO3
         cond-mat/9711094  pdf