Columbia subject headings:
Harvard subject headings:
Architecture, Modern--20th century--Pictorial works.
Architecture, Modern--21st century
Architecture--Spain--Barcelona--20th century--Guidebooks.
Architecture--Spain--Barcelona--21st century--Guidebooks.
Barcelona (Spain)--Buildings, structures, etc.
Barcelona (Spain)--Buildings, structures, etc.--Guidebooks.
Barcelona (Spain)--Buildings, structures, etc.--Pictorial works.
Princeton subject headings:
Architecture--Spain--Barcelona--20th century.
Architecture--Spain--Barcelona--21st century.
Barcelona (Spain)--Buildings, structures, etc.