APA (7e ed.) Bronvermelding

Não informado. (1960). Educators Guide to Free Science Materials. Educators Progress Service.

Chicago (17e ed.) Bronvermelding

Não informado. Educators Guide to Free Science Materials. Randolph, Wis: Educators Progress Service, 1960.

MLA (8e ed.) Bronvermelding

Não informado. Educators Guide to Free Science Materials. Educators Progress Service, 1960.

Let op: Deze citaties zijn niet altijd 100% accuraat.