Robert Curthose
Over 80 years later, David's book about the Siege of Lisbon and the "De expugnatione Lyxbonensi" remains the authoritative study, entitled "De expugnatione Lyxbonensi: The conquest of Lisbon." The book was recently revised by noted Crusades historian Jonathan Phillips for a paperback re-issue. Most of David's medieval and librarianship books remain available, if not in print. This includes Robert Curthose, Duke of Normandy (1920), a biography of Robert Curthose, the eldest son of William the Conqueror.