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On 30 September 1915 , troops of the Serbian Army observed three enemy aircraft approaching Kragujevac .
 organization: Serbian Army; location: Kragujevac
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:
 organization: Serbian Army; location: Kragujevac