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Enron  once the  United States  ' seventh-largest company entered bankruptcy proceedings in December 2001 after accounting tricks could no longer hide billions of dollars in debt .
 country of headquarters: Enron, United States
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:  Enron, United States 
Answer:
 country of headquarters: Enron, United States