1. Banko M, Cafarella M J, Soderland S, et al. Open information extraction for the web[C]//IJCAI. 2007. 7: 2670–2676.
2. Liu Jinhong, Lu Yuliang. A review of topical web crawlers [Jl. Computer Application Research, 2007, 24(10): 26–29.
3. Singhal A. Introducing the knowledge graph: things, not strings [J]. Official Google Blog, May, 2012.
4. Talking to machines
5. Lohr S. Wolfram, a Search Engine, Finds Answers Within Itself [J]. The New York Times, February, 2012, 6