Doppelblock [DOPP-5-005P]
Similar Puzzle Books
1000 Math Logic Puzzles – Collection I
US, CA; UK, DE, FR, ES, IT, other 
Puzzles in this book: Kakuro, From 1 to X, Doppelblock, Futoshiki, Sign In, Digital Battleships, Index Sums, Tenner Grid, Number Cross, and Grades.
