The summarize one piece of evidence, the 20th hijacker says he had support from the core Saudi Royal family, and listed specific individuals, along with a host of other financial evidence:
">Zacarias Moussaoui, a convicted 9/11 co-conspirator, says members of Saudi Arabia’s royal family helped finance al Qaeda in the years just prior to the 2001 terrorist attacks..."
When facing deposition, Moussaoui named specific names:
"He said in the prison deposition that he was directed in 1998 or 1999 by Qaeda leaders in Afghanistan to create a digital database of donors to the group.
Among those he said he recalled listing in the database were Prince Turki al-Faisal, then the Saudi intelligence chief; Prince Bandar Bin Sultan, the longtime Saudi ambassador to the United States; Prince al-Waleed bin Talal, a prominent billionaire investor; and many of the country’s leading clerics.
“Sheikh Osama wanted to keep a record who give money,” he said in imperfect English — “who is to be listened to or who contributed to the jihad." [Factcheck.org]
Then of course there are the charity fronts:
"Former Sen. Bob Graham, chairman at the time of the Senate Select Committee on Intelligence, called for the release of the 28 pages on the day the report was made public, Dec. 11, 2002, and still holds that position.
Graham told ABC News last month that the U.S. government’s refusal to release the 28 pages is an effort to protect Saudi Arabia, which he said is “the most responsible for that network of support.”
“The 28 pages primarily relate to who financed 9/11, and they point a very strong finger at Saudi Arabia as being the principal financier,” Graham told ABC News.