@inbook{NBERc2387,
 Crossref = "NBERuniv60-2",
 title = "An Economic Analysis of Fertility",
 author = "Gary S. Becker",
 BookTitle = "Demographic and Economic Change in Developed Countries",
 Publisher = "Columbia University Press",
 pages = "209-240",
 year = "1960",
 URL = "http://www.nber.org/chapters/c2387",
}
@book{NBERuniv60-2,
 title = "Demographic and Economic Change in Developed Countries",
 author = "George B. Roberts, Chairman, Universities-National Bureau Committee for Economic Research",
 institution = "National Bureau of Economic Research",
 type = "Book",
 publisher = "Columbia University Press",
 year = "1960",
 URL = "http://www.nber.org/books/univ60-2",
}