Microforms:

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.