@inbook{NBERc6582,
 Crossref = "NBERcost08-1",
 title = "Why the U.S. Civil War",
 author = "Dora L. Costa and Matthew E. Kahn",
 BookTitle = "Heroes and Cowards: The Social Face of War",
 Publisher = "Princeton University Press",
 year = "2008",
 month = "February",
 URL = "http://www.nber.org/chapters/c6582",
}
@book{NBERcost08-1,
 title = "Heroes and Cowards: The Social Face of War",
 author = "Dora L. Costa and Matthew E. Kahn",
 institution = "National Bureau of Economic Research",
 type = "Book",
 publisher = "Princeton University Press",
 year = "2008",
 URL = "http://www.nber.org/books/cost08-1",
}