Cita APA (7th ed.)

(1968). Populations: A science unit for the primary grades (Trial ed.). Science Curriculum Improvement Study.

Cita Chicago (17th ed.)

Populations: A Science Unit for the Primary Grades. Trial ed. Berkeley, CA: Science Curriculum Improvement Study, 1968.

Cita MLA (9th ed.)

Populations: A Science Unit for the Primary Grades. Trial ed. Science Curriculum Improvement Study, 1968.