--subdivision Audio-visual aids under subjects; and subdivision Study and teaching--Audio-visual aids under subjects for the use of audio-visual aids in the learning and teaching of those subjects, e.g. Geography--Study and teaching--Audio-visual aids
Here are entered works on patients' practical or economic access to therapeutic drugs. Works on the physiological availability of administered drugs within the body are entered under Drugs--Bioavailability.
Here are entered works on water resources both superficial and underground, primarily for domestic, manufacturing, or agricultural purposes. Works on physical and economic access to adequate water are entered under Water security. --subdivision Water-supply under topical headings
