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The F-117 used flat surfaces ( faceting technique ) for controlling radar returns as during its development ( see Lockheed Have Blue ) in the early 1970 s , technology only allowed for the simulation of radar reflections on simple , flat surfaces ; computing advances in the 1980 s made it possible to simulate radar returns on more complex curved surfaces .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
Answer:
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