Amy Shields. (2011). National Geographic Readers: Trains. National Geographic Children's Books.
Cita Chicago (17th ed.)Amy Shields. National Geographic Readers: Trains. National Geographic Children's Books, 2011.
Cita MLA (9th ed.)Amy Shields. National Geographic Readers: Trains. National Geographic Children's Books, 2011.
Atenció: Aquestes cites poden no estar 100% correctes.