It covers 30,627 km² (11,9## sq mi)
https://en.wikipedia.org/wiki/Normandy
https://en.wikipedia.org/wiki/History_of_Normandy
https://en.wikipedia.org/wiki/Duchy_of_Normandy#Origins
https://en.wikipedia.org/wiki/Treaty_of_Saint-Clair-sur-Epte
https://en.wikipedia.org/wiki/Rollo#Biography 911
