Automata with Nested Pebbles Capture First-Order Logic with Transitive Closure.

Joost Engelfriet Hendrik Jan Hoogeboom Automata with Nested Pebbles Capture First-Order Logic with Transitive Closure. 2007 3 Logical Methods in Computer Science 2 http://dx.doi.org/10.2168/LMCS-3(2:3)2007 db/journals/lmcs/lmcs3.html#EngelfrietH07