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Du Bois showcases his studies on socialism and social Darwinism as well in this work , a continuation on his examination of the genealogy of blacks outlined in The Philadelphia Negro ( 1899 ) and The Souls of Black Folk ( 1903 ) that refutes the biological differences between blacks and whites .
 person: Du Bois
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: Du Bois 
Answer:
 person: Du Bois