Columbia subject headings:
Geochemistry.
Groundwater--Africa.
Groundwater--Europe.
Mineralogy--Africa.
Mineralogy--Europe.
Harvard subject headings:
Geochemistry
Groundwater--Africa.
Groundwater--Europe.
Mineralogy--Africa.
Mineralogy--Europe.
Princeton subject headings:
Geochemistry.
Groundwater--Africa.
Groundwater--Europe.
Mineralogy--Africa.
Mineralogy--Europe.