@inbook{NBERc6786,
 Crossref = "NBERclot85-1",
 title = "Appendix G: Comparison of Aggregate Tax-Rate Variables",
 author = "Charles T. Clotfelter",
 BookTitle = "Federal Tax Policy and Charitable Giving",
 Publisher = "University of Chicago Press",
 pages = "300",
 year = "1985",
 URL = "http://www.nber.org/chapters/c6786",
}
@book{NBERclot85-1,
 title = "Federal Tax Policy and Charitable Giving",
 author = "Charles T. Clotfelter",
 institution = "National Bureau of Economic Research",
 type = "Book",
 publisher = "University of Chicago Press",
 year = "1985",
 URL = "http://www.nber.org/books/clot85-1",
}