Columbia subject headings:
Harvard subject headings:
Enlightenment--Germany
Friendship--Germany--History--18th century.
German periodicals--History--18th century.
Middle class--Germany--History--18th century.
Princeton subject headings:
Enlightenment--Germany.
Friendship--Germany--History--18th century.
German periodicals--History--18th century.
Middle class--Germany--History--18th century.