1. Department of Homeland Security [DHS] (2009). "National Infrastructure Protection Plan." Washington D.C.: Department of Homeland Security Science and Technology Division http://www.dhs.gov/national-infrastructure-protectionplan.
2. Department of Homeland Security [DHS] (2011) "Integrated Rapid Visual Screening of Tunnels." Washington D.C.: Department of Homeland Security Science and Technology Division Ref#: BIPS 03 http://www.dhs.gov/nationalinfrastructure-protection-plan.
3. Department of Homeland Security [DHS] (2013). "Building and Infrastructure Protection Series Tools." Washington D.C.: Department of Homeland Security Science and Technology Division http://www.dhs.gov/buildingand-infrastructure-protection-series-tools-0