Ranko Lazic, Joël Ouaknine, James Worrell. Zeno, Hercules and the Hydra: Downward Rational Termination Is Ackermannian. In Krishnendu Chatterjee, Jiri Sgall, editors, Mathematical Foundations of Computer Science 2013 - 38th International Symposium, MFCS 2013, Klosterneuburg, Austria, August 26-30, 2013. Proceedings. Volume 8087 of Lecture Notes in Computer Science, pages 643-654, Springer, 2013. [doi]
Abstract is missing.