Spärck Jones, K. (1972). “A Statistical Interpretation of Term Specificity and Its Application in Retrieval”. Journal of Documentation28: 11–21. doi:10.1108/eb026526.
Robertson, S. (2004). “Understanding inverse document frequency: On theoretical arguments for IDF”. Journal of Documentation60 (5): 503–520. doi:10.1108/00220410410560582.
Aizawa, Akiko (2003). “An information-theoretic perspective of tf–idf measures” (英語). Information Processing and Management39 (1): 45–65. doi:10.1016/S0306-4573(02)00021-3.