Ann Arbor-based ProQuest has acquired the International Bibliography of the Social Sciences, a database that includes more than 2.5 million bibilographic references for researchers.

IBSS adds to ProQuest's storehouse of research information, which the software company sells to academic researchers, libraries and governments.

IBSS was established in 1951 by the London School of Economics. The database includes references to books, reviews and journal articles, for example. It adds about 120,000 references annually.

“As the information world becomes more complex, the role of accurate, comprehensive (abstracting and indexing) ... becomes more essential,” said Marty Kahn, ProQuest CEO, in a statement.

ProQuest, which recently announced that it would expand its Hong Kong office, has about 550 workers in Ann Arbor.

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