McFarland, J.; Hussar, B.; Zhang, J.; Wang, X.; Wang, K.; Hein, S.; Diliberti, M.; Forrest Cataldi, E.; Bullock Mann, F.; Barmer, A. (2019). The Condition of Education 2019 (NCES 2019-144)(PDF). Washington, DC: National Center for Education Statistics: U.S. Department of Education. p. 296. สืบค้นเมื่อ 1 October 2019.