Third-neighbor and other four-point correlation functions of spin-1/2   XXZ chain
  The correlation functions of the spin-1/2 XXZ chain in the ground state were expressed in the form of multiple integrals for -1<\Delta \leq 1 and 1<\Delta. In particular, adjacent four-point correlation functions were given as certain four-dimensional integrals. We show that these integrals can be reduced to polynomials with respect to specific one-dimensional integrals. The results give the polynomial representation of the third-neighbor correlation functions. 
Go Kato, Masahiro Shiroishi, Minoru Takahashi, Kazumitsu Sakai