@inbook{NBERc1573,
 Crossref = "NBERbrad66-1",
 title = "Some Aspects of Development in the Coal Mining Industry, 1839-1918",
 author = "Vera F. Eliasberg",
 BookTitle = "Output, Employment, and Productivity in the United States after 1800",
 Publisher = "NBER",
 pages = "405-442",
 year = "1966",
 URL = "http://www.nber.org/chapters/c1573",
}
@book{NBERbrad66-1,
 title = "Output, Employment, and Productivity in the United States after 1800",
 author = "Dorothy S. Brady",
 institution = "National Bureau of Economic Research",
 type = "Book",
 publisher = "NBER",
 year = "1966",
 URL = "http://www.nber.org/books/brad66-1",
}