The accounting principles for foreign-currency transactions are defined in
Statement of Financial Accounting Standards No. 52, "Foreign-Currency Translation," in addition to several Emerging Issues Task Force papers, including EITF 90-17, "Hedging Foreign-Currency Risks with Purchased Options"; EITF 91-1, "Hedging Intercompany Foreign-Currency Risks"; and EITF 91-4, "Hedging Foreign-Currency Risks with Complex Options and Similar Transactions." Keep in mind that economically prudent hedging transactions don't always qualify for the hedge accounting prescribed in SFAS 52.