PDF - http://www.fas.org/sgp/crs/terror/RS22211.pdf
"Although the vast majority of Muslims in Europe are not involved in radical activities, Islamist extremists and vocal fringe communities that advocate terrorism exist and reportedly have provided cover for terrorist cells. Germany and Spain were identified as key logistical and planning bases for the September 11, 2001 attacks on the United States. The March 2004 terrorist bombings in Madrid have been attributed to an Al Qaeda-inspired group of North Africans. And UK authorities suspect four young British nationals with possible Al Qaeda ties of carrying out the July 7, 2005 terrorist attacks on London. This report provides an overview of Islamist extremism in Europe, possible terrorist links, European responses, and implications for the United States. It will be updated as needed.'"
