As Internet resources become accessible to more and more countries, there is a need to develop efficient methods for information retrieval across languages. In the present paper, we focus on query expansion techniques to improve the effectiveness of an information retrieval. A combination to a dictionary-based translation and statistical-based disambiguation is indispensable to overcome translation's ambiguity. We propose a model using multiple sources for query reformulation and expansion to

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... lect expansion terms and retrieve information needed by a user. Relevance feedback, thesaurus-based expansion, as well as a new feedback strategy, based on the extraction of domain keywords to expand user's query, are introduced and evaluated. We evaluated the effectiveness of the proposed combined method, by an application to a French-English Information Retrieval.