Lax pair formulation for a small-polaron chain with integrable   boundaries
  Using a fermionic version of the Lax pair formulation, we construct an integrable small-polaron model with general open boundary conditions. The Lax pair and the boundary supermatrices $K_{\pm}$ for the model are obtained. This provides a direct proof of the integrability of the model. 
Xi-Wen Guan, Uwe Grimm, and Rudolf A. Roemer