Não informado. (1991). Research and Exploration. National Geographic Society.
Chicagoスタイル(17版)引用形式Não informado. Research and Exploration. Gaithersburg, Md: National Geographic Society, 1991.
MLA(8版)引用形式Não informado. Research and Exploration. National Geographic Society, 1991.
警告: この引用は必ずしも正確ではありません.