@inbook{NBERc4253,
 Crossref = "NBERunkn69-3",
 title = "Papers Presented To The Board Of Directors At The Spring Meeting, 1969",
 author = "",
 BookTitle = "New Challenges for Economic Research",
 Publisher = "NBER",
 pages = "3-41",
 year = "1969",
 URL = "http://www.nber.org/chapters/c4253",
}
@book{NBERunkn69-3,
 title = "New Challenges for Economic Research",
 author = "NBER",
 institution = "National Bureau of Economic Research",
 type = "Book",
 publisher = "NBER",
 year = "1969",
 URL = "http://www.nber.org/books/unkn69-3",
}