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To illustrate the significance of this claim , they draw a comparison between the early twenty-first century and that of the mid-nineteenth century , famously engaged by Karl Marx , in which factory labor was dominant even if it was not the form of labor practiced by the most people .
 Karl Marx
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 Karl Marx