Box three...I assume that's bottom left?

Okay, well in my bottom left I had this (the numbers in brackets are 'little' numbers, i.e. the possibles):

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`5 (2/4) (1/2/3/7)`

6 (2/4) (1/2/3/7)

8 9 (1/2/3/7)

I had already noticed the 2/4 pair (but thanks for the tip anyway), so I can reduce to this:

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`5 (2/4) (1/3/7)`

6 (2/4) (1/3/7)

8 9 (1/3/7)

Then, using the 4/7 pair in row nine, I can further reduce to this:

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`5 (2/4) (1/3/7)`

6 (2/4) (1/3/7)

8 9 (1/3)

So, that's where I was when I got stuck.

Just in case box three is top right, here's what I've got there:

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` (6/8/9) 3 (1/8/9)`

(2/7/9) (1/9) 4

(2/6/7/8/9) (8/9) 5

If there's supposed to be an a/b pair there, then I've got something wrong.

Thanks.