ravel wrote:...i think that more than box elimination can be done with travelers: ...Possible partners are: 1: 29 ...

Its a combination of box elimination and (normal) pairs.

Let us see. You are talking about the middle vertical band, columns 456.

The condensed picture is

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`458 129 367`

12379 134689 14589

1369 123579 12489

5 is going down left, alone, since 4 and 8 are going down right. It follows that three digits go down left, alone, and six digits go down right, in pairs. 2 is going down left, hence is alone. 6 is going down left, hence is alone. We see that the three pairs are 48, 19, 37, and the picture becomes

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`458 129 367`

237 468 159

169 357 248

That excluded 13 digits in the condensed picture, a big success.

Now by line-box interactions. In box 8 digits 4,8 live in column 6,

so there is no 4 or 8 in box 5 in column 6. In box 2 digits 1,2,9 live in column 5, so there are no 1,2,9 in column 5 in box 5 or 8. This means that column 5 in box 8 has digits 3,5,7, and there are no digits 3 in column 5, box 5, or in column 4 box 8. Now in boxes 5,8 two of the three columns are known, and the third follows.

Looking at the condensed picture is the same as looking at box-line intersections.