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In page Billung:

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In the 10th century, the property of the family was centered in the Bardengau around Lüneburg and they controlled the march named after them.[citation needed] In the middle of the 10th century, when the Saxon dukes of the House of Liudolfing had also become German kings, King Otto the Great entrusted more and more of his ducal authority to Hermann Billung. For five generations, the House of Billung ruled the Duchy of Saxony.[2]