@inbook{NBERc6328,
 Crossref = "NBERbarg44-1",
 title = "Copper Mining and Ore Dressing",
 author = "Harold Barger and Sam H. Schurr",
 BookTitle = "The Mining Industries, 1899-1939: A Study of Output, Employment, and Productivity",
 Publisher = "NBER",
 pages = "222-239",
 year = "1944",
 URL = "http://www.nber.org/chapters/c6328",
}
@book{NBERbarg44-1,
 title = "The Mining Industries, 1899-1939: A Study of Output, Employment, and Productivity",
 author = "Harold Barger and Sam H. Schurr",
 institution = "National Bureau of Economic Research",
 type = "Book",
 publisher = "NBER",
 year = "1944",
 URL = "http://www.nber.org/books/barg44-1",
}