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Helicopter: (double rotor) Heinrich Focke, Germany, 1936; (single rotor) Igor Sikorsky, U.S., 1939,Jet propulsion:(engine) Sir Frank Whittle, England, Hans von Ohain, Germany, 1936; (aircraft) Heinkel He 178, 1939 and Microscope:(compound) Zacharias Janssen, The Netherlands, 1590; (electron) Vladimir Zworykin et al., U.S., Canada, Germany, 1932-1939

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15y ago

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