UN R81 (1989)
18 Sep 1989 2011-01-28 17:06:41 UTC
UN R81 (1998)
7 May 1998 2011-01-28 17:07:42 UTC
UN R81 (2007)
7 Aug 2007 2011-01-28 17:24:56 UTC
Earlier texts may be available through the UN Official Document System.