In this paper we present BR-Explorer, a sound and complete biological data sources retrieval algorithm based on Formal Concept Analysis and domain ontologies. BR-Explorer addresses the problem of retrieving the relevant data sources for a given query. Initially, a formal context representing the relation between biological data sources and their metadata is provided and its corresponding concept lattice is built. Then BR-Explorer starts by generating the formal concept for the considered query and inserting it into the provided concept lattice. The next step of BR-Explorer is to locate the "pivot" concept in the resulting concept lattice. Based on this pivot concept, BR-Explorer builds the result step by step by considering the pivot superconcepts in the resulting concept lattice until the top concept is reached. Finally BR-Explorer provides the set of relevant data sources ranked according to their relevance with respect to the considered query. An ontology-based query refinement procedure is integrated in BR-Explorer. This procedure takes advantage of semantic information about the data source metadata and the queries to improve the BR-Explorer results.