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The Marian army constitutes the transition from the Manipular Roman army ( ca. 300-107 BC ) , which was a temporary force based on adult male conscription of citizens to the Imperial Roman army of the Principate , which was a standing , professional force based mainly on volunteer recruitment .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
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