aeb wrote:(1,6)2 is ruled out as follows:

If (1,6)2 then (456,6)468 and (789,5)2478, but four digits cannot be in three cells.

But if (1,6)2 then (123,5)368 and (789,5)247 ... so I have doubts that your elimination is valid.

(123,5)2368 and (789,5)2478 are doubly-weakly-linked ALSs and share the 2 and the 8. We just don't know which set will hold which. But we do know neither set must hold both ... no matter what happens at (1,6).

Ron