Akrivi Katifori Elena Torou Costas Vassilakis Giorgos Lepouras Constantin Halatsis Selected results of a comparative study of four ontology visualization methods for information retrieval tasks. 133-140 2008 RCIS http://dx.doi.org/10.1109/RCIS.2008.4632101 conf/rcis/2008 db/conf/rcis/rcis2008.html#KatiforiTVLH08