BLUEBIRD BOOKS. (2001). CHILDREN'S REFERENCE: PLANET EARTH.
Cita Chicago (17th ed.)BLUEBIRD BOOKS. CHILDREN'S REFERENCE: PLANET EARTH. 2001.
Cita MLA (9th ed.)BLUEBIRD BOOKS. CHILDREN'S REFERENCE: PLANET EARTH. 2001.
Atenció: Aquestes cites poden no estar 100% correctes.