From Sudopedia, the free Sudoku reference guide
Killer Notation
From Sudopedia
Killer Sudokus are notated similarly to normal sudokus. The only additional notation that needs to be learned is identifying cages. Cages are identified by their size and sum rather than position. A cage of 17/4 also 17(4) or 17[4] or 17{4}, is a cage with a sum of 17 and a size of 4 cells. If more than one cage fits this description, then a relative location is given along with it to clarify: 17/4 on N6. This clarifies that the 17/4 that is referenced is the one on nonet(block) 6 (assuming only one 17/4 is on N6). Another popular way to notate killer sudokus is to give the upper left-hand corner of the cage: 17/4 at r4c7.
