Karen Kemp. Encyclopedia of Geographic Information Science. SAGE.
Lua i Stíl Chicago (17ú heag.)Karen Kemp. Encyclopedia of Geographic Information Science. SAGE.
Lua MLA (8ú heag.)Karen Kemp. Encyclopedia of Geographic Information Science. SAGE.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.