Columbia subject headings:
Bombings--Prevention--Congresses.
Drug control--Congresses.
Environmental monitoring--Congresses.
Explosives--Congresses.
Optical detectors--Congresses.
X-rays--Scattering--Congresses.
Harvard subject headings:
Princeton subject headings:
Electronic security systems--Congresses.
Electronics in crime prevention--Congresses.
Optical detectors--Congresses.