(1968). Populations: A science unit for the primary grades (Trial ed.). Science Curriculum Improvement Study.
芝加哥风格引文Populations: A Science Unit for the Primary Grades. Trial ed. Berkeley, CA: Science Curriculum Improvement Study, 1968.
MLA引文Populations: A Science Unit for the Primary Grades. Trial ed. Science Curriculum Improvement Study, 1968.
警告：这些引文格式不一定是100％准确.