“…According to the different choices of L and ∂ x , we have nine types of telescopers in general, see Table 1. The existence problem of telescopers is related to the termination of Zeilbergerstyle algorithms and has been studied in [8,6,17,15] but, to our knowledge, our results concerning telescopers of the six types underlined in the above table are new. In this section, we will present a unified way to solve this problem for rational functions by using the knowledge in the previous sections.…”