I have a Google doc document. Using Edit->File->See Revision History I can see older revisions and go to them. I want to give some-one a URL which points directly to a specific revision of my document which is not the current one. How do I do this?

(Note: The link from the revision list does not work outside that list, if you enter it in the address bar you just get the list, not the document; the URL in the address bar when you load the older revision does not work either)