“…The language modeling framework was first introduced by Ponte and Croft [19], followed by many research activities related to this framework since then [1, 3, 4, 8, 10-12, 14-18, 20, 21, 23]. For example, query expansion techniques [3,11,12,17,18,21,23], pseudo-relevance feedback [4,11,12,17,18,21,23], parameter estimation methods [10], multi-word features [20], passage segmentations [16] and time constraints [14] have been proposed to improve the language modeling frameworks. Among them, query expansion with pseudo feedback can increase retrieval performance significantly [11,18,23].…”