Here is an article written by Steve McConnell for IEEE Software, Vol. 13, No. 2, March 1996, that you might find helpful:

Missing in Action: Information Hiding

You should be able to glean some arguments for encapsulation from this article.

Also, McConnell's book Code Complete has an excellent section on information hiding. It is section 6.2 in the old edition. Looking at the contents of the new edition, it looks like it is in section 5.3,but I haven't read it so I can't verify if that is true.

All developers should have a copy of Code Complete (well worn from reading of course) sitting on their desks. Smiley

Hope this is helpful.

~Bebo