Não informado. (1969). Science activities. Science Activities Publishing.
Chicago-Zitierstil (17. Ausg.)Não informado. Science Activities. Washington: Science Activities Publishing, 1969.
MLA-Zitierstil (8. Ausg.)Não informado. Science Activities. Science Activities Publishing, 1969.
Achtung: Diese Zitate sind unter Umständen nicht zu 100% korrekt.