Sudoku #3651

Complexity: Extremely Hard

 Fun Fact About Sudoku
Wayne Gould, New Zealander and retired Hong Kong judge, calls himself the stepfather of Sudoku. He stumbled upon a Sudoku book in Tokyo while vacationing there.

Enter numbers into the empty cells so that each row, column and 3x3 box contains the numbers 1 to 9.

1 8 2 3
8 5 9 1 7
3 1 8
1 6 5 7 9 3 8
8 7 2 3 6 9
9 4 1 8 6 5 2
5 8 9
9 8 4 2 7
4 1 9 8