@techreport{NBERw12973,
 title = "The Benefits and Costs of Head Start",
 author = "Jens Ludwig and Deborah A. Phillips",
 institution = "National Bureau of Economic Research",
 type = "Working Paper",
 series = "Working Paper Series",
 number = "12973",
 year = "2007",
 month = "March",
 URL = "http://www.nber.org/papers/w12973",
}