Peter, Go to http://www.tlg.uci.edu/Uni.prop.html, the web site of Thesaurus Linguae Graecae (who made the formal proposals) to see the actual proposals. Basically these 13 are the editorial signs used in the Nestle-Aland edition of the NT, a digital version of which is in progress. I am working on a font with these characters (and I think one is already available from SIL).
David
