@inbook{NBERc1708,
 Crossref = "NBERtroy65-1",
 title = "Sources and Methods of Deriving Union Membership Statistks Since 1934",
 author = "Leo Troy",
 BookTitle = "Trade Union Membership, 1897-1962",
 Publisher = "NBER",
 pages = "10-17",
 year = "1965",
 URL = "http://www.nber.org/chapters/c1708",
}
@book{NBERtroy65-1,
 title = "Trade Union Membership, 1897-1962",
 author = "Leo Troy",
 institution = "National Bureau of Economic Research",
 type = "Book",
 publisher = "NBER",
 year = "1965",
 URL = "http://www.nber.org/books/troy65-1",
}