Heyneman, S. P. (1978). Textbooks and achievement: What we know. World Bank.
Lua i Stíl Chicago (17ú heag.)Heyneman, Stephen P. Textbooks and Achievement: What We Know. Washington: World Bank, 1978.
Lua MLA (9ú heag.)Heyneman, Stephen P. Textbooks and Achievement: What We Know. World Bank, 1978.
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