Sudoku – the fear of all sums

Sir, – Could you consider an occasional article explaining the technique employed to solve some of your harder sudoku puzzles?

The sudokus that appeared on the June 2nd and 3rd were, to me at least, quite difficult, and I had to leave them unsolved. Bridge players benefit from your periodic Bridge Notes column. It would be good to see something similar in the sudoku section. – Yours, etc,

JOE RYAN,