Currency valuation (with respect to other currencies) is an important parameter in finance, but how is it related to the cash reserve ratio?
Here's a little bit of everything.
1) Some papers on foreign reserves that are used to defend a country's currency, and the flexibility of their exchange rate:
2) Some papers on generic modeling of exchange rates:
Figure 1 in the above link is a common view of the short/medium/long-term variables that affect exchange rates.
3) If you're trying to play with exchange rates as a retail investor, you need to be aware of the game/scams: