1. Bertoldi, N. and M. Federico, 2000. Italian text retrieval for CLEF 2000 at ITC-irst. In Working notes of CLEF 2000. Lisbon, Portugal.
2. Johnson, S.E., P. Jourlin, K. Spark Jones, and P.C. Woodland, 1999. Spoken document retrieval for TREC-8 at Cambridge University. In Proc. of 8th TREC. Gaithersburg, MD.
3. Miller, David R. H., Tim Leek, and Richard M. Schwartz, 1998. BBN at TREC-7: Using hidden Markov models for information retrieval. In Proc. of 7th TREC. Gaithersburg, MD.
4. Ney, Herman, Ute Essen, and Reinhard Kneser, 1994. On structuring probabilistic dependences in stochastic language modelling. Computer Speech and Language, 8:1–38.
5. Ng, Kenney, 1999. A maximum likelihood ratio information retrieval model. In Proc. of 8th TREC. Gaithersburg, MD.