@inbook{NBERc10045,
 Crossref = "NBERgril84-1",
 title = "The Rate of Obsolescence of Patents, Research Gestation Lags, and the Private Rate of Return to Research Resources ",
 author = "Ariel Pakes and Mark Schankerman",
 BookTitle = "R & D, Patents, and Productivity",
 Publisher = "University of Chicago Press",
 pages = "73-88",
 year = "1984",
 URL = "http://www.nber.org/chapters/c10045",
}
@book{NBERgril84-1,
 title = "R & D, Patents, and Productivity",
 author = "Zvi Griliches",
 institution = "National Bureau of Economic Research",
 type = "Book",
 publisher = "University of Chicago Press",
 year = "1984",
 URL = "http://www.nber.org/books/gril84-1",
}