The 1914-1818war.com project has drawn upon many source materials. Many of these are reviewed below.
Here is a list of the reviews available
The First World War by Hew Strachan review.
Castles Of Steel: Britain, Germany and the Winning of The Great War at Sea by Robert K Massie.
The Challenge of Battle by Adrian Gilbert review.
The Illustrated War Reports – Trench Warfare by Bob Carruthers.
Verdun the Left bank by Christina Holstein