@inbook{NBERc10689,
 Crossref = "NBERgrub01-1",
 title = "The Sexual Activity and Birth-Control Use of American Teenagers",
 author = "Phillip B. Levine",
 BookTitle = "Risky Behavior among Youths: An Economic Analysis",
 Publisher = "University of Chicago Press",
 pages = "167-218",
 year = "2001",
 month = "January",
 URL = "http://www.nber.org/chapters/c10689",
}
@book{NBERgrub01-1,
 title = "Risky Behavior among Youths: An Economic Analysis",
 author = "Jonathan Gruber",
 institution = "National Bureau of Economic Research",
 type = "Book",
 publisher = "University of Chicago Press",
 year = "2001",
 URL = "http://www.nber.org/books/grub01-1",
}