@inbook{NBERc5731,
 Crossref = "NBERunkn51-1",
 title = "Part X Estimating the Number of Earners for Income Size Distribution Analysis",
 author = "Emmett Welch",
 BookTitle = "Studies in Income and Wealth",
 Publisher = "NBER",
 pages = "560-572",
 year = "1951",
 URL = "http://www.nber.org/chapters/c5731",
}
@book{NBERunkn51-1,
 title = "Studies in Income and Wealth",
 author = "Lillian Epstein, editor and Martha Anderson, editor",
 institution = "National Bureau of Economic Research",
 type = "Book",
 publisher = "NBER",
 year = "1951",
 URL = "http://www.nber.org/books/unkn51-1",
}