Tax burden in USA. Question.

Last night a very RW guy looked up on the interwebs and said that over half of Federal taxes were paid by the top 5% of Americans. He said it was the Treasury Dept. website. I went to find it today and can't. I DID find a 2005 House study that agreed with what he was saying, but it applied only to the top 5% of INCOME, which I suspect means "wages." It did not include estates, capital gains etc. etc.

Can anyone tell me if their is a reliable and authoritative source that explains the tax burden in this country?

the progressive tax structure of the U.S. federal income tax system on individuals that reduces the tax incidence of people with smaller incomes, as they shift the incidence disproportionately to those with higher incomes - the top 0.1% of taxpayers by income pay 17.4% of federal income taxes (earning 9.1% of the income), the top 1% with gross income of $328,049 or more pay 36.9% (earning 19%), the top 5% with gross income of $137,056 or more pay 57.1% (earning 33.4%), and the bottom 50% with gross income of $30,122 or less pay 3.3% (earning 13.4%).<9><10> If the federal taxation rate is compared with the wealth distribution rate, the net wealth (not only income but also including real estate, cars, house, stocks, etc) distribution of the United States does almost coincide with the share of income tax - the top 1% pay 36.9% of federal tax (wealth 32.7%), the top 5% pay 57.1% (wealth 57.2%), top 10% pay 68% (wealth 69.8%), and the bottom 50% pay 3.3% (wealth 2.8%).<11>'

http://en.wikipedia.org/wiki/Taxation_in_the_United_States#Tax_distribution

...and it is only accessible with a subscription.