Columbia subject headings:
Postcards--History--19th century.
Postcards--History--20th century.
Sorbs--Pictorial works.
Sorbs--Social life and customs--Pictorial works.
Harvard subject headings:
Postcards--History--19th century.
Postcards--History--20th century.
Sorbs--Pictorial works.
Sorbs--Social life and customs--Pictorial works.
Princeton subject headings: