Sudoku #3781

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.

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