In a letter to Adalbero, Bishop of Laon, Dudo said that, as a result, Richard asked him to write a work recording "the customs and deeds of the Norman Land, the rights established within the kingdom of his great-grandfather Rollo".
[4] Written between 996 and 1015, his Historia Normannorum—also known as Libri III de moribus et actis primorum Normanniae ducum and Gesta Normannorum—was dedicated to Adalberon, bishop of Laon.
Dudo does not appear to have consulted any existing documents for his history, but to have obtained his information from oral tradition, much of it being supplied by Raoul, count of Ivry, a maternal half-brother of Duke Richard.
[citation needed] Other authorities, such as Jules Lair and Johannes Steenstrup, while admitting the existence of a legendary element, regard the book as of considerable value for the history of the Normans.
The Historia, which is written alternately in prose and in verse of several metres, is divided into four parts, and deals with the history of the Normans from 852 to the death of Duke Richard in 996.