History 24 Juvenile literature 7 World War, 1939-1945 7 Biography 5 Politics and government 5 Airplanes, Military 4 Encyclopedias 4 Fighter planes 4 Helicopters 4 International relations 4 20th century 3 Campaigns 3 Examinations 3 Management 3 Naval art and science 3 Philosophy 3 Sea-power 3 United States 3 Warships 3 Yearbooks 3 21st century 2 Aeromatics 2 Aeronautics 2 Air-ships 2 Airplanes 2 Corvettes (Warship) 2 Destroyers (Warship 2 Economic conditions 2 Frigates 2 Generals 2