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These include models to study the electronic properties of solids , such as the Drude model , the band structure and the density functional theory .
 person: Drude
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: Drude 
Answer:
 person: Drude