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A union representing workers at Olympic Airlines said Tuesday it opposes the prospect of  Qatar Airways  buying  Greece  's troubled state-owned carrier .
 country of headquarters: Qatar Airways, Greece
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:  Qatar Airways, Greece 
Answer:
 country of headquarters: Qatar Airways, Greece