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The Thomas–Fermi theory , developed in the 1920 s , was used to estimate system energy and electronic density by treating the local electron density as a variational parameter .
 person: Thomas–Fermi
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: Thomas–Fermi 
Answer:
 person: Thomas–Fermi