@inbook{NBERc1869,
 Crossref = "NBERseid64-1",
 title = "Appendix C Trends in Credit Ratings",
 author = "Martin H. Seiden",
 BookTitle = "The Quality of Trade Credit",
 Publisher = "UMI",
 pages = "116-126",
 year = "1964",
 URL = "http://www.nber.org/chapters/c1869",
}
@book{NBERseid64-1,
 title = "The Quality of Trade Credit",
 author = "Martin H. Seiden",
 institution = "National Bureau of Economic Research",
 type = "Book",
 publisher = "UMI",
 year = "1964",
 URL = "http://www.nber.org/books/seid64-1",
}