Re: Difference and Duality

Hi, Posina, I have downloaded "Conceptual Mathematics" and will look at it and your question later, but in the meantime, I hope that others will respond more quickly and directly to your question. However, in case you do not receive adequate replies on Linked, may I suggest two other forums which may be more fruitful. http://mathematica.stackexchange.com/ and sometimes http://www.physicsforums.com/forumdisplay.php?s=6f5ea9f0f093fb645c4a319aad65a89c&f=78 Both require registration, but they are free and do not seem to generate spam. David Reid [For admin and other information see: http://www.mta.ca/~cat-dist/ ]