1. An introduction to the syntax and content of cyc;Matuszek,2006
2. Wordnet: a lexical database for english;Miller;Commun. ACM,1995
3. Dbpedia: a nucleus for a web of open data;Auer,2007
4. Freebase: A collaboratively created graph database for structuring human knowledge;Bollacker,2008
5. Representing general relational knowledge in conceptnet 5;Speer,2012