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On June 19 , 2008 , Philadelphia City Councilman Darrell Clarke introduced changes for the zoning legislation around 18th and Arch Streets which was the first step towards building the tower .
 Philadelphia, Darrell Clarke
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Philadelphia, Darrell Clarke