@inbook{NBERc6959,
 Crossref = "NBERgold92-1",
 title = "Structural Change in the Farm Labor Force: Contract Labor in Massachusetts Agriculture, 1750-1865",
 author = "Winifred B. Rothenberg",
 BookTitle = "Strategic Factors in Nineteenth Century American Economic History: A Volume to Honor Robert W. Fogel",
 Publisher = "University of Chicago Press",
 pages = "105-134",
 year = "1992",
 month = "January",
 URL = "http://www.nber.org/chapters/c6959",
}
@book{NBERgold92-1,
 title = "Strategic Factors in Nineteenth Century American Economic History: A Volume to Honor Robert W. Fogel",
 author = "Claudia Goldin and Hugh Rockoff",
 institution = "National Bureau of Economic Research",
 type = "Book",
 publisher = "University of Chicago Press",
 year = "1992",
 URL = "http://www.nber.org/books/gold92-1",
}