although too late to be evidence for 10th-century practice. The late 11th-century Norman historian William of Poitiers used the title "Count of Rouen" for the Norman rulers down to Richard II. According to David C. Douglas, the title "Count of Rouen" (comes Rotomagensis) was never used in any official document. Charters are usually a source of information about titles, but none exist for Normandy in the middle of the tenth century.

The first official recorded use of the title duke (dux) is