@inbook{NBERc3919,
 Crossref = "NBERkend80-1",
 title = "Returns to Research and Development Expenditures in the Private Sector",
 author = "Zvi Griliches",
 BookTitle = "New Developments in Productivity Measurement",
 Publisher = "University of Chicago Press",
 pages = "419-462",
 year = "1980",
 URL = "http://www.nber.org/chapters/c3919",
}
@book{NBERkend80-1,
 title = "New Developments in Productivity Measurement",
 author = "John W. Kendrick and Beatrice N. Vaccara",
 institution = "National Bureau of Economic Research",
 type = "Book",
 publisher = "University of Chicago Press",
 year = "1980",
 URL = "http://www.nber.org/books/kend80-1",
}