Dario Carotenuto Aniello Murano Adriano Peron 2-Visibly Pushdown Automata. 132-144 2007 conf/dlt/2007 Developments in Language Theory http://dx.doi.org/10.1007/978-3-540-73208-2_15 db/conf/dlt/dlt2007.html#CarotenutoMP07