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However , sociological forces possibly related to their sparse populations and dependence on robot labor lead to the collapse of most of these worlds ; their dominance is replaced by new , upstart colonies known as Settler worlds in the Milky Way galaxy .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
Answer:
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