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Previously , U . S . officials had said they were uncertain whether North Korea had received enough outside technical help to even attempt to make such a ` ` miniaturized ' ' nuclear warhead .
 U . S, North Korea, U . S . officials, they, such a ` ` miniaturized ' ' nuclear warhead
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: organization, person, geographical social political, vehicle, location, weapon, facility 
Text: {0} 
Answer:
 U . S, North Korea, U . S . officials, they, such a ` ` miniaturized ' ' nuclear warhead