Pawel Parys. A Pumping Lemma for Pushdown Graphs of Any Level. In Christoph Dürr, Thomas Wilke, editors, 29th International Symposium on Theoretical Aspects of Computer Science, STACS 2012, February 29th - March 3rd, 2012, Paris, France. Volume 14 of LIPIcs, pages 54-65, Schloss Dagstuhl - Leibniz-Zentrum fuer Informatik, 2012. [doi]
Abstract is missing.