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They asked him to please find a way to stop this future plan , but not knowing exactly what form their plan would take they said that he must be vigilant and keep his eyes open , because they could not be certain how the technology their sons were developing would be used to implement it .
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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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