1. Wikidata: A free collaborative knowledge base;Vrandečić;CACM,2014
2. DBpedia: A nucleus for a web of open data;Auer,2007
3. Yago: A core of semantic knowledge;Suchanek,2007
4. Introducing the knowledge graph: things, not strings;Singhal,2012
5. Inconsistencies, negations and changes in ontologies;Flouris,2006