Fidel Cacheda Victor Carneiro Carmen Guerrero Ángel Viña Optimization of Restricted Searches in Web Directories Using Hybrid Data Structures. 436-451 2003 conf/ecir/2003 ECIR https://doi.org/10.1007/3-540-36618-0_31 db/conf/ecir/ecir2003.html#CachedaCGV03