V.E. Adler. A Mathematica implementation of the generalized summation by parts algorithm. (2014)
 Download:
psum.zip (readme.pdf, psum.nb, psum.m, examples.nb, tests.nb, Yamilov.nb)
 Last revised: 25 March 2015 (ver.1.2)
 Mathematica version: 5, works for 8
 Description:
An algorithm for solving of difference equations of the form
T^{m}(y)  ay = b
with variable coefficients, where T denotes the shift operator. Solvability
of such type of equations with respect to the coefficients of formal symmetry
(or formal recursion operator) provides a convenient integrability
test for evolutionary differentialdifference equations
u_{t} = f(u_{m},...,u_{m}).
 Ref: http://arxiv.org/abs/1408.5726v1
