Sudoku X - 120 Easy To Master Puzzles 8x8 - 5 - John Collins - Bog

Sudoku X also called Diagonal Sudoku.The puzzle is a 8x8 grid made up of 4x2 subgrids (called "regions").Some cells already contain numbers, known as "givens".The goal is to fill in the empty cells, one number in each, so that each column, row, region and diagonal contains the numbers 1 through 8 exactly once.Each number in the solution therefore occurs only once in each of three "directions", hence the "single numbers" implied by the puzzle's name.