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Varian Medical Systems  of  Palo Alto  California made its first linear accelerator optimized for stereotactic radiosurgery in 1992 called the Clinac 600SR .
 city of headquarters: Varian Medical Systems, Palo Alto
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:  Varian Medical Systems, Palo Alto 
Answer:
 city of headquarters: Varian Medical Systems, Palo Alto