Não informado. (1990). Cartography and geographic information systems. American Congress on Surveying and Mapping.
Chicago-viite (17. p.)Não informado. Cartography and Geographic Information Systems. Bethesda, Md: American Congress on Surveying and Mapping, 1990.
MLA-viite (8. p.)Não informado. Cartography and Geographic Information Systems. American Congress on Surveying and Mapping, 1990.
Varoitus: Nämä viitteet eivät aina ole täysin luotettavia.