Nelson, D. (1997). Student Study Guide to Accompany Environmental Science: A Global Concern (4th ed.). WCB/McGraw-Hill.
Cita Chicago (17th ed.)Nelson, Darby. Student Study Guide to Accompany Environmental Science: A Global Concern. 4th ed. Boston: WCB/McGraw-Hill, 1997.
Cita MLA (9th ed.)Nelson, Darby. Student Study Guide to Accompany Environmental Science: A Global Concern. 4th ed. WCB/McGraw-Hill, 1997.
Atenció: Aquestes cites poden no estar 100% correctes.