Columbia subject headings:
Harvard subject headings:
Postal service--Germany--Rhineland-Palatinate--History--Bibliography.
Rhineland-Palatinate (Germany)--History--Bibliography.
Transportation--Germany--Rhineland-Palatinate--History--Bibliography.
Princeton subject headings:
Postal service--Germany--Rhineland-Palatinate--History--Bibliography.
Rhineland-Palatinate (Germany)--History--Bibliography.
Transportation--Germany--Rhineland-Palatinate--History--Bibliography.