Elisabeth M. C. van Houts, in The Normans in Europe, edited by Elisabeth M. C. van Houts (Manchester: Manchester University Press, 2000). ©2000, Elisabeth M. C. van Houts. — 41 — The Plaintsong (Planctus) of William Longsword was composed shortly after his murder in 943 instigated by Count Arnulf I of Flanders. The poem, which survives in two manuscripts, has never been properly edited and presents many linguistic and historical problems. It was composed either at Jumièges in Normandy or, more likely, considering the southern French provenance of the manuscripts, under the patronage of William's sister Gerloc/Adela, countess of Aquitaine and Poitou. As a contemporary text it is one of the most important sources for information about Rollo's dynasty.