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His early death left a power vacuum that resulted in the disastrous civil war between his Empress-dowager , Anna of Savoy , and his closest friend and supporter , John VI Kantakouzenos .
 Anna of Savoy, John VI Kantakouzenos
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Anna of Savoy, John VI Kantakouzenos