Calvin, C. (1991). Themes in geography: International issues. Hodder & Stoughton.
Cita Chicago (17th ed.)Calvin, Clarke. Themes in Geography: International Issues. London: Hodder & Stoughton, 1991.
Cita MLA (9th ed.)Calvin, Clarke. Themes in Geography: International Issues. Hodder & Stoughton, 1991.
Atenció: Aquestes cites poden no estar 100% correctes.