Tim Berners-Lee, Larry Masinter, and Mark McCahill, December 1994, RFC 1738: Uniform Resource Locators (URL).
Tim Howes, Mark Smith, and Frank Dawson, September 1998, RFC 2425: A MIME Content-Type for Directory Information.
Frank Dawson and Tim Howes, September 1998, RFC 2426: vCard MIME Directory Profile.