The Bielefeld Academic Search Engine contains more than 30 million scientific
documents, full texts and references of books and articles, most of which are freely
accessible. This search engine offers intellectually selected resources, and includes only
document servers that comply with the specific requirements of academic quality and
relevance. It provides "Refine your search result" opinions (by author, subject, DDC, year of publication, content provider, language, document type, access and terms of re-use).