@inbook{NBERc11891,
 Crossref = "NBERglae09-1",
 title = "Breakthrough Inventions and Migrating Clusters of Innovation",
 author = "William R. Kerr",
 BookTitle = "Cities and Entrepreneurship",
 Publisher = "Journal of Urban Economics, Vol. 67, no. 1",
 year = "2010",
 month = "January",
 URL = "http://www.nber.org/chapters/c11891",
}
@book{NBERglae09-1,
 title = "Cities and Entrepreneurship",
 author = "Edward L. Glaeser and Stuart S. Rosenthal and William C. Strange",
 institution = "National Bureau of Economic Research",
 type = "Book",
 publisher = "Journal of Urban Economics, Vol. 67, no. 1",
 year = "2010",
 URL = "http://www.nber.org/books/glae09-1",
}