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When Moffat took over Davies ' duties as executive producer , he began expanding on the character 's background , depicting adventures earlier in River 's timeline , upgrading Alex Kingston from a guest star to a recurring actor in the series .
 Moffat, Davies, Alex Kingston
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Moffat, Davies, Alex Kingston