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The origins of the Pittsburgh Glass Center date to 1991 , when David Stephens , then visual-arts officer of the Pennsylvania Council on the Arts , approached glass artists Ron Desmett and Kathleen Mulcahy , then a professor at Carnegie Mellon University , about the idea of a center for studio glass .
 Pittsburgh, Pennsylvania, Carnegie Mellon University
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Pittsburgh, Pennsylvania, Carnegie Mellon University