Boston, home to institutions such as Harvard and MIT, again came in second, followed by Tokyo, which moved from fourth to third this year.Five cities entered the top 20 this year, including Pittsburgh, Vienna, Vancouver, Philadelphia, and Munich.TOP SEATS OF LEARNINGThe 2008 Global University City IndexCity Country Rank '08 ('07)London Britain 1 (1)Boston US 2 (2)Tokyo Japan 3 (4)Melbourne Austral