a) as documents were prepared for the 9/11 Commission (or the Senate or the President himself), that person was screening possibly embarassing items and alerting Lindsey;
b) Lindsey got the ex-Clinton administration figure (like Berger) involved to ask for a "review" of the documents (for accuracy, of course);
c) the former Clinton administration officials then pulled or replaced incriminating documents before the 9/11 Commission or anyone else could see them;
Berger was just too lazy and/or arrogant to bring replacements, or the missing documents could not be covered up.
The most frightening thing is we have no idea if Berger's case is an isolated example of former Clinton administration officials.
If it is not, and if many people in government in different departments (CIA, FBI, Satte, etc.) were involved in pre-screening and deep-sixing documents, then neither the 9/11 Commission nor the Senate Committees ever saw the whole truth.
It's also quite possible that no one in the present administation has seen the whole truth either.
that person= the person at the National Archives who alerted Clinton's lawyer Lindsey
I agree, this most likely goes much deeper.