@inbook{NBERc2623,
 Crossref = "NBERlong58-1",
 title = "Males in the Labor Force over Time",
 author = "Clarence D. Long",
 BookTitle = "The Labor Force Under Changing Income and Employment",
 Publisher = "Princeton University Press",
 pages = "144-158",
 year = "1958",
 URL = "http://www.nber.org/chapters/c2623",
}
@book{NBERlong58-1,
 title = "The Labor Force Under Changing Income and Employment",
 author = "Clarence D. Long",
 institution = "National Bureau of Economic Research",
 type = "Book",
 publisher = "Princeton University Press",
 year = "1958",
 URL = "http://www.nber.org/books/long58-1",
}