Freeland, P. (1991). Habitats and the enviornment. Hedder&Stoughton.
Cita Chicago (17th ed.)Freeland, Peter. Habitats and the Enviornment. London: Hedder&Stoughton, 1991.
Cita MLA (9th ed.)Freeland, Peter. Habitats and the Enviornment. Hedder&Stoughton, 1991.
Atenció: Aquestes cites poden no estar 100% correctes.