Não informado. (1990). Geo info systems. Advanstar Communications.
Chicagoスタイル(17版)引用形式Não informado. Geo Info Systems. Duluth, Minn: Advanstar Communications, 1990.
MLA(8版)引用形式Não informado. Geo Info Systems. Advanstar Communications, 1990.
警告: この引用は必ずしも正確ではありません.