A similar entry appears in the Wheel of Time Companion confirming the information available in the main story arc.
Author: Kyria d'Oreyn
Sorelana Alsahhan was a scholar during the Trolloc Wars who wrote of "The hundred packs the Shadow's hounds that hunt the night". Masuri cites this as she tells Perrin and the others of the Darkhounds that had passed outside his camp.
(Reference: Crossroads of Twilight, Chapter 27).