Reference:
Accounting Trends and Techniques published annually by the AICPA

Hope this helps.

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Note added at 3 hrs (2009-01-14 17:27:14 GMT)
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Accounting Trends & Techniques - 2008 edition
Page 331 / ATT-SEC 3.42
Income Taxes
We recognize deferred tax assets and liabilities for the future tax consequences attributable to differences between the financial statements carrying amounts of existing assets and liabilities and their respective tax bases. A valuation allowance is provded when it is more likely than not that some portion or all of a deferred tax asset will not be realized. The ultimate realization of deferred tax assets depends on the generation of future TAXABLE INCOME during the period in which the related temporary differences become deductible. We consider the scheduled reversal of deferred tax liabilities, projected future TAXABLE INCOME and tax planning strategies in this assessment. Deferred tax assets and liabilities are measured using the enacted tax rates expected to apply to TAXABLE INCOME in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income of the period that includes the enactment date of such change.