Reference:
 - Author: George A. Miller
   Title: "WordNet: A Lexical Database for English"
   Journal: Communications of the ACM
   Year: 1995
   Volume: 38
   Number: 11
   Pages: 39-41
   DOI: 10.1145/219717.219748
   URL: http://dl.acm.org/citation.cfm?id=219748
 - Author: Christiane Fellbaum
   Title: "WordNet: An Electronic Lexical Database"
   Journal: MIT Press
   Year: 1998
   URL: http://mitpress.mit.edu/catalog/item/default.asp?ttype=2&tid=8106
 - Author: Christiane Fellbaum
   Title: WordNet and wordnets
   Year: 2005
   In: "Brown, Keith et al. (eds.), Encyclopedia of Language and Linguistics, Second Edition, Oxford: Elsevier, 665-670"
