By Michael.Czapski on Feb 24, 2010
For these who have a need, the HL7 v 2.3.1 standard document is available online at http://www.medclinic.net/HL7Specs/ as at February 24, 2010. The site does not seems to have been updated for a long time so the standard document may well be available for a while longer.
HL7 v 2.3 document is available at http://www.uhc.com.pl/teksty/HL7/, again, as at February 24, 2010.
IHE Europe has an interesting "interactive" site where HL7 can be "explored" at http://ihe.univ-rennes1.fr/HL7/.