1. V. Porter: Continuous library catalog card, Patent 4005810 (1976), This represents a computer-area patent on the original library catalog card.
http://www.google.com/patents?vid=USPAT4005810
(last accessed 2009)
2. T.-A. Wong: Card catalogs and card catalog drawers, Patent 5257859 (1993), This represents a tweak on the original design of the card catalog drawer.
http://www.google.com/patents?vid=USPAT5257859
(last accessed 2009)
3. University of Pennsylvania: Cards from rapidly-disappearing card catalog. (Philadelphia 2008),
http://www.library.upenn.edu/exhibits/pennhistory/library/cards/cards.samples.html
(last accessed 2009)
4. Online Computer Library Center (OCLC): OCLC catalog cards. (Dublin 2008),
http://www.oclc.org/support/documentation/worldcat/cataloging/cards/default.htm
(last accessed 2009)
5. K. Coyle: Catalogs, card – and other anachronisms, J. Acad. Librarians 31(1), 60–62 (2005)