APA (7th ed.) Citation

Cox, A. B., & Gifford, F. (1997). An Overview of Geographic Information Systems.

Chicago Style (17th ed.) Citation

Cox, Allan B., and Fred Gifford. An Overview of Geographic Information Systems. 1997.

MLA (9th ed.) Citation

Cox, Allan B., and Fred Gifford. An Overview of Geographic Information Systems. 1997.

Warning: These citations may not always be 100% accurate.