Walker Sally M. (2010). Early Bird Earth Science Volcanoes. Lerner.
Cita Chicago (17th ed.)Walker Sally M. Early Bird Earth Science Volcanoes. Lerner, 2010.
Cita MLA (9th ed.)Walker Sally M. Early Bird Earth Science Volcanoes. Lerner, 2010.
Atenció: Aquestes cites poden no estar 100% correctes.