Exact Results of the 1D $1/r^2$ Supersymmetric t-J Model without   Translational Invariance
  In this work, we continue the study of the supersymmetric t-J model with 1/r^2 hopping and exchange without translational invariance. A set of Jastrow wavefunctions are obtained for the system, with eigenenergies explicitly calculated. The ground state of the t-J model is included in this set of wavefunctions. The spectrum of this t-J model consists of equal-distant energy levels which are highly degenerate. 
C. Gruber and D. F. Wang