Columbia subject headings:
Art, Prehistoric--Conservation and restoration--Portugal--Côa River Valley.
Côa River Valley (Portugal)--Antiquities.
Petroglyphs--Conservation and restoration--Portugal--Côa River Valley.
Plein air painting--Conservation and restoration--Portugal--Côa River Valley.
Rock paintings--Conservation and restoration--Portugal--Côa River Valley.
Harvard subject headings:
Art, Prehistoric--Conservation and restoration--Portugal--Côa River Valley.
Petroglyphs--Conservation and restoration--Portugal--Côa River Valley.
Plein air painting--Conservation and restoration--Portugal--Côa River Valley.
Rock paintings--Conservation and restoration--Portugal--Côa River Valley.
Princeton subject headings:
Art, Prehistoric--Conservation and restoration--Portugal--Côa River Valley.
Côa River Valley (Portugal)--Antiquities.
Petroglyphs--Conservation and restoration--Portugal--Côa River Valley.
Plein air painting--Conservation and restoration--Portugal--Côa River Valley.
Rock paintings--Conservation and restoration--Portugal--Côa River Valley.