Title: The early 20th century
Subjects: World War, 1914-1918, Discoveries in science, World War, 1939-1945, Technological innovations, Technology, History, Technology, juvenile literature, Discoveries in science, juvenile literature, World war, 1939-1945, World war, 1939-1945, juvenile literature, World war, 1914-1918, World war, 1914-1918, juvenile literature
Time periods: 20th century