Não informado. (1960). Educators Guide to Free Science Materials. Educators Progress Service.
Chicagoスタイル(17版)引用形式Não informado. Educators Guide to Free Science Materials. Randolph, Wis: Educators Progress Service, 1960.
MLA(8版)引用形式Não informado. Educators Guide to Free Science Materials. Educators Progress Service, 1960.
警告: この引用は必ずしも正確ではありません.