@inbook{NBERc12272,
 Crossref = "NBERannu23-1",
 title = "Annual Report of the Director of Research",
 author = "Wesley C. Mitchell",
 BookTitle = "Annual Report of the Director of Research",
 Publisher = "NBER",
 pages = "1-12",
 year = "1923",
 month = "February",
 URL = "http://www.nber.org/chapters/c12272",
}
@book{NBERannu23-1,
 title = "Annual Report of the Director of Research",
 author = "Wesley C. Mitchell",
 institution = "National Bureau of Economic Research",
 type = "Book",
 publisher = "NBER",
 year = "1923",
 URL = "http://www.nber.org/books/annu23-1",
}