This chapter presents a new bibliothecal structure and its application. A vital precondition for the success of any system of information retrieval that may be devised, whether computer-assisted or not, is that the source material that it identifies as satisfying enquirers requests should be readily located by them in the library. The solution demands no less than recognition of the existence of a “third world” of literature or, to use another metaphor, that the two main protagonists that have held the stage for so long—books and serials—should be joined by a third, named documents and reports. There is no conceptual purity in the existing nomenclature. All that is required is a consensus as to what a documents and reports collection (as distinct from a book or serials collection) should comprise.