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In 1903 – 1904 Jacob Ellehammer used his experience constructing motorcycles to build the world 's first air-cooled radial engine , a three-cylinder engine which he used as the basis for a more powerful five-cylinder model in 1907 .
 Jacob Ellehammer
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 Jacob Ellehammer