Tamar Aizikowitz Michael Kaminski Conjunctive Grammars and Alternating Pushdown Automata. 44-55 2008 WoLLIC http://dx.doi.org/10.1007/978-3-540-69937-8_6 conf/wollic/2008 db/conf/wollic/wollic2008.html#AizikowitzK08