In FY 1021, Lothair Mantelar founds the Children of the Light to combat the increasing number of Darkfriends. He publishes his philosophy in a book, The Way of the Light. (Guide, TEotW,Glossary, TSR,Ch17)
Other References
TSR,Ch17 - Eamon Valda gives Galad a copy of Lothair Mantelar's book, The Way of the Light, and he starts becoming interested in the Whitecloaks.
ToM,Ch40 � Galad quotes Lothair Mantelar that he cannot be blamed for actions of the Shadow.