Carcul wrote:You mean that those puzzles can't be solved with the techniques you describe in your book?
The techniques described in my book are enough to solve all of the puzzles in it. Trial and error is one of those techniques. It describes both forward and backward propagation styles of T&E, and also advanced T&E which goes beyond the logic of just singles--though that only has been found to appear in two puzzles so far to my knowledge, neither of them officially listed in the book. (The toughest known puzzle is shown, but it is not technically one of the 150 puzzles.)
Then your book must be an interesting one. If he will someday arrive to Portugal then I will take a look at it.
Lulu.com does offer shipping to Portugal. They ship there in 5-15 days for economy shipping, 5-10 for standard, 3-7 express.