1. Apache OpenNLP Development Community. (2012). Apache OpenNLP developer documentation. The Apache Software Foundation, 1.5.2 edition.
2. Baeza-Yates, R., & Ribeiro-Neto, B. (2011). Modern information retrieval: The concepts and technology behind search (2nd edn.). Addison-Wesley.
3. Bentley, J., Knuth, D., & McIlroy, D. (1986). Programming pearls. Communications of the ACM, 6(29), 471–483.
4. Bourne, S. R. (1982). The unix system. International computer science series. Addison-Wesley.
5. Brin, S., & Page, L. (1998). The anatomy of a large-scale hypertextual web search engine. Computer Networks, 30(1–7), 107–117. Proceedings of WWW7.