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He took over there , and took control of the red button controlling nuclear arms , in December 1991 when Mikhail Gorbachev resigned , marking the end of the Soviet Union .
 person: Mikhail Gorbachev; location: Soviet Union
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: location, else, organization, person 
Text: {0} 
Answer:
 person: Mikhail Gorbachev; location: Soviet Union