Estes, J. S. ;. J. (1990). Geographic Information Systems An Introduction. Prentice Hall.
Lua i Stíl Chicago (17ú heag.)Estes, Jeffrey Star ; John. Geographic Information Systems An Introduction. Prentice Hall, 1990.
Lua MLA (8ú heag.)Estes, Jeffrey Star ; John. Geographic Information Systems An Introduction. Prentice Hall, 1990.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.