@inbook{NBERc6508,
 Crossref = "NBERwill32-1",
 title = "Fixed Medical Service In the Coal Mining Industry of the Rocky Mountain States ",
 author = "Pierce Williams",
 BookTitle = "The Purchase of Medical Care Through Fixed Periodic Payment",
 Publisher = "NBER",
 pages = "112-123",
 year = "1932",
 URL = "http://www.nber.org/chapters/c6508",
}
@book{NBERwill32-1,
 title = "The Purchase of Medical Care Through Fixed Periodic Payment",
 author = "Pierce Williams",
 institution = "National Bureau of Economic Research",
 type = "Book",
 publisher = "NBER",
 year = "1932",
 URL = "http://www.nber.org/books/will32-1",
}