@inbook{NBERc7983,
 Crossref = "NBERglae08-1",
 title = "Urbanization, Agglomeration, and Co-Agglomeration of Service Industries",
 author = "Jed Kolko",
 year = "2007",
 month = "December",
 URL = "http://www.nber.org/chapters/c7983",
}