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The Philadelphia dialect, which is spread throughout the Delaware Valley and South Jersey, is part of Mid-Atlantic American English, and as such it is identical in many ways to the Baltimore dialect. Unlike the Baltimore dialect, however, the Philadelphia accent also shares many similarities with the New York accent. Thanks to over a century of linguistics data collected by researchers at the University of Pennsylvania, the Philadelphia dialect under sociolinguist William Labov has been one of the best-studied forms of American English.[f]

Who studies the accent at the University of Pennsylvania?
William Labov