Oscar H. Ibarra, Juhani Karhumäki, Alexander Okhotin. On Stateless Multihead Automata: Hierarchies and the Emptiness Problem. In Eduardo Sany Laber, Claudson F. Bornstein, Loana Tito Nogueira, Luerbio Faria, editors, LATIN 2008: Theoretical Informatics, 8th Latin American Symposium, Búzios, Brazil, April 7-11, 2008, Proceedings. Volume 4957 of Lecture Notes in Computer Science, pages 94-105, Springer, 2008. [doi]
Abstract is missing.