How to secure FA Books with Operating Unit(s)

Hi Folks,

I have two Operating Unit(s)..

1) ABC,,

2) XYZ..

Under ABC OU, I have two Asset Books named as Asset-Book1 and Asset-Book2.

Under XYZ OU, I have one Asset Book named as Asset-Book3,.

Now problem is that, When I'm going through XYZ Responsibility.. User have the visibility of Asset-Book3 as well as Asset-Book2 but not Asset-Book1. (Asset-Book1 & Asset-Book2 are under the Operating Unit of 'ABC')

Can you please let me know,, How to restrict Asset-Book2 from XYZ Responsibility. In-short, XYZ have different operating unit and should have the visibility of just 'Asset-Book3'.

Thanks-