@inbook{NBERc3278,
 Crossref = "NBERhans70-1",
 title = "The Production of Human Capital Over Time",
 author = "Yorman Ben-Porath",
 BookTitle = "Education, Income, and Human Capital",
 Publisher = "NBER",
 pages = "129-154",
 year = "1970",
 URL = "http://www.nber.org/chapters/c3278",
}
@book{NBERhans70-1,
 title = "Education, Income, and Human Capital",
 author = "W. Lee Hansen",
 institution = "National Bureau of Economic Research",
 type = "Book",
 publisher = "NBER",
 year = "1970",
 URL = "http://www.nber.org/books/hans70-1",
}