1. A method comprising: receiving a set of development sentences W; receiving a set of language models G M ; determining a set of n-gram language model weights λ M based on the development sentences W and the set of language models G M ; determining a set of sentence cluster weights γ C , each of the sentence cluster weights corresponding to a cluster in a set of sentence clusters, each cluster in the set of sentence clusters associated with at least one sentence from the set of development sentences W; and generating a language model from the set of language models G M , the set of n-gram language model weights λ M , the set of sentence clusters, and the set of sentence cluster weights γ C .