(1968). Populations: A science unit for the primary grades (Trial ed.). Science Curriculum Improvement Study.
Chicago-viite (17. p.)Populations: A Science Unit for the Primary Grades. Trial ed. Berkeley, CA: Science Curriculum Improvement Study, 1968.
MLA-viite (9. p.)Populations: A Science Unit for the Primary Grades. Trial ed. Science Curriculum Improvement Study, 1968.
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