oorlog : hoe wij er voor staan en wat wij deden / door Winston Spencer Churchill, Earl Kitchener en David Lloyd George ; redevoeringen gehouden … British Secret Service during the Great War / by Nicholas Everitt ; [with a foreword by Northcliffe] secret corps : a tale of "intelligence" on all fronts / by Ferdinand Tuohy work of the Royal Engineers in the European war, 1914-19 / Royal Engineers Institute. Secretary : Supply of engineer stores and equipment