Portion of FX in a portfolio?

[amado]

I'm trying to locate any background information/papers/analysis which looks at (and recommends) FX as part of an investment portfolio. I'm familiar with something from Deutsche Bank from a couple of years ago, but apart from that I find it hard to locate anything online - and I don't feel like a total dummy with Google either.

So, if you have any pointers/links I'd be grateful.