▪ Dirichlet prior smoothing (LM-DIR) ▪ Jelinek Mercer smoothing (LM-JM) - Information-Based Model[3] (IB) 13 [1] Stephen E, et al. The Probabilistic Relevance Framework: BM25 and Beyond. Foundations and Trends in Information Retrieval. 2009. [2] ChengXiang Zhai and John D. Lafferty. A Study of Smoothing Methods for Language Models Applied to Ad Hoc Information Retrieval. SIGIR. 2001. [3] Stéphane Clinchant and Éric Gaussier. Information-based models for ad hoc IR. SIGIR. 2010.