Percentage Distribution of 6- to 12-year-olds, 1972-97. US Department of Education.
Chicago-viite (17. p.)Percentage Distribution of 6- to 12-year-olds, 1972-97. US Department of Education.
MLA-viite (9. p.)Percentage Distribution of 6- to 12-year-olds, 1972-97. US Department of Education.
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