@inbook{NBERc7639,
 Crossref = "NBERcutl01-1",
 title = "IV Extensions of the Frontier",
 author = "",
 BookTitle = "Medical Care Output and Productivity",
 Publisher = "University of Chicago Press",
 pages = "509-510",
 year = "2001",
 month = "January",
 URL = "http://www.nber.org/chapters/c7639",
}
@book{NBERcutl01-1,
 title = "Medical Care Output and Productivity",
 author = "David M. Cutler and Ernst R. Berndt",
 institution = "National Bureau of Economic Research",
 type = "Book",
 publisher = "University of Chicago Press",
 year = "2001",
 URL = "http://www.nber.org/books/cutl01-1",
}