-- See Also the narrower term Chemical detectors Here are entered works on apparatus used to detect the presence or absence of chemicals on a relatively gross scale in industrial processes, environmental protection, etc.
-- See Also the narrower term Remote sensing Here are entered works on the theory or methodology of collecting and gathering images of distant objects or property. Works on handling, maintaining, and indexing remote-sensing images in unbound collections are entered under Remote-sensing images. --subdivision Remote sensing under topical headings