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Four men were killed in central  Vietnam  when a bomb left over from the war exploded along the former  Ho Chi Minh  Trail an official said Wednesday .
 country of headquarters: Vietnam, Ho Chi Minh
Given options, please tell me the relationships of all the listed entity pairs.Output format is "relation1: word1, word2; relation2: word3, word4". 
Option: cities of residence, top members employees, members, alternate names, origin, state or provinces of residence, title of person, spouse, city of headquarters, NA, founded by, state or province of headquarters, employee of, countries of residence, country of birth, founded, subsidiaries, country of headquarters 
Text: {0} 
 Entity Pairs:  Vietnam, Ho Chi Minh 
Answer:
 country of headquarters: Vietnam, Ho Chi Minh