This excerpt taken from the MT 20-F filed Feb 20, 2009.
Use of estimates
The preparation of financial statements in conformity with IFRS recognition and measurement principles and, in particular, making the aforementioned critical accounting judgments require the use of estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses. Management reviews its estimates on an ongoing basis using currently available information. Changes in facts and circumstances may result in revised estimates, and actual results could differ from those estimates.