Sudoku

This puzzle has several solutions:

x x x | 4 5 6 | 7 8 9
4 5 6 | 7 8 9 | 1 2 3
7 8 9 | 1 2 3 | 4 5 6
- - - - - - - - - - -
x x x | 5 6 4 | 8 9 7
5 6 4 | 8 9 7 | 2 3 1
8 9 7 | 2 3 1 | 5 6 4
- - - - - - - - - - -
x x x | 6 4 5 | 9 7 8
6 4 5 | 9 7 8 | 3 1 2
9 7 8 | 3 1 2 | 6 4 5

and if we pick away numbers, all solutions above will still be solutions to the puzzle! Thus we can get a 17 clue sudoku with several solutions.