(2000). Percentage Distribution of 6- to 12-year-olds, 1972-97. U.S. Department of Education.
Chicago-viite (17. p.)Percentage Distribution of 6- to 12-year-olds, 1972-97. U.S. Department of Education, 2000.
MLA-viite (9. p.)Percentage Distribution of 6- to 12-year-olds, 1972-97. U.S. Department of Education, 2000.
Varoitus: Nämä viitteet eivät aina ole täysin luotettavia.