1. American Council on Education. (2010a). GED testing service? http://www.acenet.edu/AM/Template.cfm?Section=GED_TS.
2. American Council on Education. (2010b). History of the GED tests. http://www.acenet.edu/Content/NavigationMenu/ged/about/history.htm.
3. Abortion and selection;Ananat;Review of Economics and Statistics,2009
4. Schooling and labor market consequences of the 1970 state abortion reforms;Angrist;Research in Labor Economics,1999
5. The impact of grading standards on student achievement, educational attainment, and entry-level earnings;Betts;Economics of Education Review,2003