This excerpt taken from the VOD 20-F filed Jun 14, 2007.
Use of Estimates
The preparation of financial statements in accordance with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Estimates are used for, but not limited to, the accounting for: allowances for uncollectible accounts receivable, unbilled revenue, fair values of financial instruments, depreciation and amortization, useful lives and impairment of assets, accrued expenses, inventory reserves, equity in income of unconsolidated entities, employee benefits, income taxes, contingencies and allocation of purchase prices in connection with business combinations. Estimates and assumptions are periodically reviewed and the effects of any material revisions are reflected in the consolidated financial statements in the period that they are determined to be necessary.