Guillaume Bagan Arnaud Durand Etienne Grandjean On Acyclic Conjunctive Queries and Constant Delay Enumeration. 208-222 2007 conf/csl/2007 CSL http://dx.doi.org/10.1007/978-3-540-74915-8_18 db/conf/csl/csl2007.html#BaganDG07