As said earlier, supply is another basic factor. Supply means availability of documents for acquisition. Information regarding supply can be collected in the form of various selection sources or tools. A detailed discussion on a variety of selection tools, their characteristics, value and importance for selection of printed documents and non-print materials is given in Unit 6 of this Block 2. The library will be regularly receiving various source materials. If not, they have to be acquired. A good source collection may contain the following:
• Trade catalogues issued by individual publishers and booksellers • Book trade journals • Previews and announcements issued by publishers • Book reviews appearing in newspapers and journals • Book reviewing journals • Book selection lists brought out by competent bodies • List of textbooks prescribed for various courses of studies • Published catalogues of book exhibitions • Published catalogues of important libraries • Subject bibliographies and subject guides to selection
• National bibliographies
• Comprehensive retrospective bibliographies like BooksinPrint
• Catalogues of second-hand booksellers
The sources have to be sorted and stored for convenient use. Updating of the sources and weeding out of old ones should be done on a regular basis.