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This approach was continued by Russell and Whitehead in their influential " Principia Mathematica " , first published 1910 – 1913 , and with a revised second edition in 1927 .
 person: Russell; person: Whitehead
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
 Entities: Russell, Whitehead 
Answer:
 person: Russell; person: Whitehead