1National Center for Education Statistics (NCES). The Con-dition of Education 2003 [R]. Institute of Education Sci-ences, NCES2003-067, Washington, D.C., 2003.
2National Center for Education Statistics (NCES). Digest ofEducation Statistics 2001 [R]. Office of Educational Re-search and Improvement, NCES2002-130, Washington, D.C., 2002.