Micropublishing is retrospective, being merely the reprinting of previously existing materials. Back files of newspapers, periodicals and out-of-print materials are available in microfilms. Scientific journal publishers were experimenting with publishing their journals both in hard copy, i.e., paper-print, and also in microprint. This has not been a success, although some journals are available in both the formats. Technical reports are available in microfiche, particularly in subject fields where a large number of such reports are produced. Technical and research reports in nuclear science and agricultural sciences are available in microfiche.
Another type of original publications of increasing importance to libraries are the bibliographies and catalogues produced by the computer-output-microfilm (COM) method. In this, computerised data is reproduced on microfilm or mocrofiche without first being produced in paper-print form. COM products, such as the British Library's Books in English, are now being produced on a mass scale.
But as mentioned, microforms can be used only with microfilm or microfiche readers. These cannot be owned by individuals and therefore they will have to visit the library for making use of them. Some of the guides to microforms that can be used as selection tools are:
Guide to microforms in print, published by Meckler Publishing
National Registrar of Microforms Masters published by the Library of Congress. Both these titles are international in scope, cover commercial sources and non-commercial supplies such as those produced by libraries and historical associations. Besides these, major producers of microforms have extensive catalogues of their products. Libraries interested in the selection and acquisition of microforms may have to keep a file of these catalogues, by acquiring them directly from the producers.