Emmanuel Bruno Nicolas Faessel Hervé Glotin Jacques Le Maitre Michel Scholl Indexing by permeability in block structured web pages. 70-73 2009 ACM Symposium on Document Engineering http://doi.acm.org/10.1145/1600193.1600209 conf/doceng/2009 db/conf/doceng/doceng2009.html#BrunoFGMS09