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These experts point out that the Gregorian calendar started in 1 AD and therefore , centuries ' millennia start with a one , not a zero .
 person: These experts
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: geographical social political, organization, person, location, facility, vehicle, weapon 
Text: {0} 
 Entities: These experts 
Answer:
 person: These experts