Frame Sudoku [FRSU-2-007P]
Similar Puzzle Books
1000 Math Logic Puzzles – Collection II
US, CA; UK, DE, FR, ES, IT, other 
Puzzles in this book (mainly Sudoku variants): Calcudoku, Sudoku XV, Vudoku, Mathrax, Sandwich Sudoku, Killer Sudoku, Terra X, Little Unique Killer Sudoku, Frame Sudoku, and Sum Skyscrapers.
