A Guide to information sources (or a bibliographic guide, a literature guide, a guide to reference materials, a subject gateway, etc.) is a kind of metabibliography. Ideally it is not just a listing of bibliographies, reference works and other information sources, but more like a textbook introducing users to the information sources in a given field (in general). Such guides may have many different forms: Comprehensive or highly selective, printed or electronic sources, annoteted listings or written chapters etc.