Columbia subject headings:
German language--Middle High German, 1050-1500--Dialects--Germany--Duisburg.
German language--Middle High German, 1050-1500--Dialects--Germany--Essen.
German language--Middle High German, 1050-1500--Dialects--Germany--Venlo.
German language--Middle High German, 1050-1500--Written German.
Harvard subject headings:
German language--Middle High German, 1050-1500--Dialects--Germany--Ruhr (Region)
German language--Middle High German, 1050-1500--Graphemics.
German language--Middle High German, 1050-1500--Phonology.
Princeton subject headings:
German language--Dialects--Germany--Duisburg--History.
German language--Dialects--Germany--Essen--History.
German language--Dialects--Netherlands--Venlo--History.