Columbia subject headings:
Agriculture--Societies, etc.--Directories.
Arid regions--Research.
Science--Societies, etc.--Directories.
Harvard subject headings:
Agriculture--Societies, etc.--Directories.
Arid regions--Research
Science--Societies, etc.--Directories.
Princeton subject headings:
Agriculture--Societies, etc.--Directories.
Arid regions--Research.
Directories.
Science--Societies, etc.--Directories.