@inbook{NBERc11161,
 Crossref = "NBERchal99-1",
 title = "A Behavioral Economic Analysis of Polydrug Abuse in Heroin Addicts",
 author = "Nancy M. Petry and Warren K. Bickel",
 BookTitle = "The Economic Analysis of Substance Use and Abuse: An Integration of Econometrics and Behavioral Economic Research",
 Publisher = "University of Chicago Press",
 pages = "213-250",
 year = "1999",
 month = "January",
 URL = "http://www.nber.org/chapters/c11161",
}
@book{NBERchal99-1,
 title = "The Economic Analysis of Substance Use and Abuse: An Integration of Econometrics and Behavioral Economic Research",
 author = "Frank J. Chaloupka and Michael Grossman and Warren K. Bickel and Henry Saffer",
 institution = "National Bureau of Economic Research",
 type = "Book",
 publisher = "University of Chicago Press",
 year = "1999",
 URL = "http://www.nber.org/books/chal99-1",
}