1. Tim Berners-Lee Jean-Francois Groff and Robert Cailliau. "Universal Document Identifiers on the Network." CERN February 1992. On-line location: info.cern.ch:/pub/www/ doc/udil.ps Tim Berners-Lee Jean-Francois Groff and Robert Cailliau. "Universal Document Identifiers on the Network." CERN February 1992. On-line location: info.cern.ch:/pub/www/ doc/udil.ps
2. Brewster Kahle. "Document Identifiers or International Standard Book Numbers for the Electronic Age." Version 2.2 September 1991. On-line location: quake.think.com:/pub/wais/ doc/doc-ids.txt Brewster Kahle. "Document Identifiers or International Standard Book Numbers for the Electronic Age." Version 2.2 September 1991. On-line location: quake.think.com:/pub/wais/ doc/doc-ids.txt
3. The Universal Standard Book Number (USBN): why, how and a progress report
4. Theodore H. Nelson. Literary Machines Edition 87.1. (San Antonio Texas: Theodor H. Nelson: 1987). Theodore H. Nelson. Literary Machines Edition 87.1 . (San Antonio Texas: Theodor H. Nelson: 1987).