Multiwingspan Sudoku
Hidden Pairs

In the image, the cells marked with a red dot are the only cells in their minisquare that have 5 & 8 as candidates. Since every minisquare needs to contain all of the numbers 1-9, these two cells have to be one of these two values. We can safely eliminate all other candiates from these two cells.

We call this strategy hidden pairs because the pair of values is 'hidden' by the other candidates in these cells.

Sudoku Grid