I'm not clear on what you're getting at here. It seems doubtful that you're claiming that the existance of the Aug 6th pdb - or its content - is an unsubstantiated allegation, because the full text of same has been published.

Text: President's Daily Brief on Aug. 6, 2001 from the Washington Post, Saturday April 10, 2004.

Declassified and approved for release the same day as its publication, the PDB begins...

Bin Laden Determined to Strike in US

Clandestine, foreign government, and media reports indicate Bin Ladin since 1997 has wanted to conduct terrorist attacks in the US. Bin Ladin implied in US television interviews in 1997 and 1998 that his followers would follow the example of World Trade Center bomber Ramzi Yousef and "bring the fighting to America."

After US missile strikes on his base in Afghanistan in 1998, Bin Ladin told followers he wanted to retaliate in Washington, according to a ...(redacted portion) ... service.

An Egyptian Islamic Jihad (EIJ) operative told an ... (redacted portion) ... service at the same time that Bin Ladin was planning to exploit the operative's access to the US to mount a terrorist strike.

The existance of the PDB is substantiated, as is its content. Just for the record, and to clarify your remark, what is it about the Aug 6 PDB that you considered an "unsubstantiated allegation?"

S