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He was the acting director of the Cerro Tololo Interamerican Observatory , then president of the Associated Universities for Research in Astronomy from 1968 until 1971 , and was appointed Director of the University of Michigan Detroit Observatory in 1970 , a post he held until 1982 .
 Observatory, Michigan, Observatory
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Observatory, Michigan, Observatory