APA
Ritter M. E., . (1997). Earth online. Belmont, CA: Wadsworth Publishing Co.
Chicago
Ritter Michael E, . 1997. Earth online. Belmont, CA: Wadsworth Publishing Co.
Harvard
Ritter M. E., . (1997). Earth online. Belmont, CA: Wadsworth Publishing Co.
MLA
Ritter Michael E, . Earth online. Belmont, CA: Wadsworth Publishing Co. 1997.