Extended Subset Principle
An equal number of cells and candidate digits has one digit spanning two houses. That digit goes from outside cells seeing all of its occurrences.
How it works on this board
The number of cells equals the number of candidate digits, with only 5 spanning both houses
9
6
1
7
6
5
3
8
6
3
2
5
3
8
6
3
4
8
7
2
7
2
1
8
2
9
7
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