@article{jones72astatistical,
	title = {A statistical interpretation of term specificity and its application in retrieval},
	author = {Karen Spärck Jones},
	journal = {Journal of Documentation},
	number = {1},
	url = {http://www.soi.city.ac.uk/~ser/idfpapers/ksj_orig.pdf},
	volume = {28},
	year = {1972},
	biburl = {http://www.bibsonomy.org/bibtex/227a90e3c10346e7731081582b18fff4b/hkorte},
	description = {A statistical interpretation of term specificity and its application in retrieval},
	keywords = {nlp text_mining }
}

@article{j:idf,
	title = {A Statistical Interpretation of Term Specificity and its Application
  in Retrieval},
	author = {Karen {Sparck Jones}},
	journal = {Journal of Documentation},
	number = {1},
	pages = {11--21},
	volume = {28},
	year = {1972},
	biburl = {http://www.bibsonomy.org/bibtex/256383537fc8baccc6b6d687e028485e4/nlp},
	keywords = {2000 book nlp }
}