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Eugen Ewig (1969) thinks it might have originally been a large Merovingian "duca...
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Eugen Ewig (1969) thinks it might have originally been a large Merovingian "ducatus", defining the "core" of what had been the old Roman civitas of Tongeren ("Die Stellung Ribuariens in der Verfassungsgeschichte des Merowingerreichs ".)