Killer Sudoku, Difficulty 3

Puzzle 3961 Aug 7 August 2011
Puzzle 3971 Aug 9 August 2011
Puzzle 3981 Aug 11 August 2011
Puzzle 3991 Aug 13 August 2011
Puzzle 4001 Aug 15 August 2011
Puzzle 4011 Aug 17 August 2011
Puzzle 4021 Aug 19 August 2011
Puzzle 4031 Aug 21 August 2011
Puzzle 4041 Aug 23 August 2011
Puzzle 4051 Aug 25 August 2011
Daily Killer Sudoku