Dear Bill, Your post to me about TB has vanished into cyber-thin air. I printed out a coppy to show my daughter, and the original just vanished somewhere into the mysterious workings of this computer! However, I do have the hard copy, and I thank you very much. I did actually know all the things you said, but as usual, you wrote it so clearly and so succinctly as to make it easy to understand, and perfect for me to explain it all to my daughter. Thank y ou. DId you once mentioin that your mother was an English teacher? So was mine - but I wish I also shared your gift of clarity of mind and expression. You have a wonderful way with words, and I always look forward to reading your explanations. Thanks again, Hilary Blue