A Refined Denominator Bounding Algorithm for Multivariate Linear   Difference Equations
  We continue to investigate which polynomials can possibly occur as factors in the denominators of rational solutions of a given partial linear difference equation.   In an earlier article we had introduced the distinction between periodic and aperiodic factors in the denominator, and we gave an algorithm for predicting the aperiodic ones. Now we extend this technique towards the periodic case and present a refined algorithm which also finds most of the periodic factors. 
Manuel Kauers and Carsten Schneider
cs.SC