Laurie Mylorie gets my vote as most knowledgeable here.
If you haven't read her; "The Trade Center Bomb: Who Was Ramzi Yousef; and why it matters", I highly recommend it.
As you read it remember, it was written in 1995 - 6 years before 911! An amazing piece of work.
http://www.fas.org/irp/world/iraq/956-tni.htm