Learn / Specialty reference
Sudoku technique · Specialty reference · reference
Grouped AICs
A node can mean that a digit occurs somewhere within a defined set of cells. Links must apply to that entire group.
How to spot it
A box-line intersection is a useful first grouped node.
The common mistake
Do not transfer a single-cell visibility rule to a group without checking every member.
Learn this first
AIC.
Further reading: hodoku.sourceforge.net