tracking changes in outside documentation

[Carrie Baker]

Our company has bought 2 or 3 software applications or parts of them
which are integrated in our applications in some way.
We have received their source files in FrameMaker to put in our
FrameMaker template. In one book we took sections from theirs and
reformatted, another used one chapter reformatted and a third used
sections here and there that we added to.
Obviously they will update their software and their files will change
and they will send them to us again, and then we will need to find out
what they changed.
How is the best way for us to work together,? How should we ask them
to mark the changes made in the documentation?
I am sure we are not the only company who does this, what do other people do?
thanks


-- 
Carrie Baker
carriebak at gmail.com