Alan - here's a link that you may enjoy that provides great explanations of some of the advanced sudoku techniques and gives you the opportunity to try them out:

http://www.scanraid.com/sudoku.htm?bd=90...731200003090004

My favourite sudoku books, for those who have begun to get bored by regular "difficult" sudoku, are the Mensa Absolutely Nasty Sudoku, by Frank Longo. There are four levels. The first two are pretty straightforward, requiring only basic skills. But levels three and four use the advanced techniques that you can learn about from the link above. Those are challenging enough to make me forget pain.

Wendy

Rheumatoid Arthritis
Methotrexate, Celebrex, Plaquenil