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 http://arxiv.org/abs/cs/0703079 2007 CoRR abs/cs/0703079 db/journals/corr/corr0703.html#abs-cs-0703079 informal publication