Existence Problem of Telescopers: Beyond the Bivariate Case
  In this paper, we solve the existence problem of telescopers for rational functions in three discrete variables. We reduce the problem to that of deciding the summability of bivariate rational functions, which has been solved recently. The existence criteria we present is needed for detecting the termination of Zeilberger's algorithm to the function classes studied in this paper. 
Shaoshi Chen and Qing-Hu Hou and George Labahn and Rong-Hua Wang
cs.SC math.CO