Columbia subject headings:
Aachener Dom.
Mosaics, Carolingian--Germany--Aachen.
Harvard subject headings:
Aachen (Germany)--Buildings, structures, etc.
Aachener Dom.
Church buildings--Germany--Aachen.
Mosaics, Carolingian--Germany--Aachen.
Mosaics--Germany--Aachen.
Princeton subject headings:
Aachener Dom.
Mosaics--Germany--Aachen.