"Uniform Resource Locators", Tim Berners-Lee, January 1992. URL=ftp://info.cern.ch/pub/www/doc/url7a.ps or http://info.cern.ch/hypertext/WWW/Addressing/Addressing.html
"Protocol for the Retrieval and Manipulation of Texual and Hypermedia Information", Tim Berners-Lee, 1993. URL=ftp://info.cern.ch/pub/www/doc/http-spec.ps or http://info.cern.ch/hypertext/WWW/Protocols/HTTP/HTTP2.html
"The SGML Handbook", Charles F. GoldFarb, pub. 1990 by the Clarendon Press, Oxford.