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Allied successes were marred by the collision of two Royal Navy helicopters over the Persian Gulf in which all six British crew members and one American were killed .
 British, Royal Navy, all six British crew members, one American, two Royal Navy helicopters, the Persian Gulf
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:
 British, Royal Navy, all six British crew members, one American, two Royal Navy helicopters, the Persian Gulf