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In the mid-18 th century a group of economic theorists , led by David Hume ( 1711 – 1776 ) and Adam Smith ( 1723 – 1790 ) , challenged fundamental mercantilist doctrines - such as the belief that the world 's wealth remained constant and that a state could only increase its wealth at the expense of another state .
 person: David Hume; person: Adam Smith
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: David Hume, Adam Smith 
Answer:
 person: David Hume; person: Adam Smith