@inbook{NBERc3159,
 Crossref = "NBERmill52-1",
 title = "Conclusion",
 author = "Frederick C. Mills",
 BookTitle = "Productivity and Economic Progress",
 Publisher = "NBER",
 pages = "21-22",
 year = "1952",
 URL = "http://www.nber.org/chapters/c3159",
}
@book{NBERmill52-1,
 title = "Productivity and Economic Progress",
 author = "Frederick C. Mills",
 institution = "National Bureau of Economic Research",
 type = "Book",
 publisher = "NBER",
 year = "1952",
 URL = "http://www.nber.org/books/mill52-1",
}