Many thanks. It seems to require application of a rather strange type of logic to get to the meaning of by having two instances of the symbol which denotes [a]!
I agree and I am glad they don't write the clues for crossword puzzles (or do they for the Times? ) It makes me wonder about "any" logical thought process of the people who came up with such a system. To be fair it is possibly the result of "harmonizing" a range of different standards and symbols (though that may be being too fair)
As an aside, here is a list of xformer symbols.
http://www.google.co.uk/#hl=en&suge...gc.r_pw.&fp=9bc2c12fe7b1c385&biw=1012&bih=730