Percentage Distribution of 6- to 12-year-olds, 1972-97. US Department of Education.
Chicago-referens (17:e uppl.)Percentage Distribution of 6- to 12-year-olds, 1972-97. US Department of Education.
MLA-referens (9:e uppl.)Percentage Distribution of 6- to 12-year-olds, 1972-97. US Department of Education.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.