@inbook{NBERc3170,
 Crossref = "NBERmitc51-1",
 title = "Varieties of Reference-Cycle Amplitude",
 author = "Wesley Clair Mitchell",
 BookTitle = "What Happens During Business Cycles: A Progress Report",
 Publisher = "NBER",
 pages = "100-184",
 year = "1951",
 URL = "http://www.nber.org/chapters/c3170",
}
@book{NBERmitc51-1,
 title = "What Happens During Business Cycles: A Progress Report",
 author = "Wesley Clair Mitchell",
 institution = "National Bureau of Economic Research",
 type = "Book",
 publisher = "NBER",
 year = "1951",
 URL = "http://www.nber.org/books/mitc51-1",
}