(2000). Trends in Science Performance of 9-, 13-, & 17-year olds. U.S. Department of Education.
Chicago Style aipamenaTrends in Science Performance of 9-, 13-, & 17-year Olds. U.S. Department of Education, 2000.
MLA aipamenaTrends in Science Performance of 9-, 13-, & 17-year Olds. U.S. Department of Education, 2000.
Kontuz: berrikusi erreferentzia hauek erabili aurretik.