Cita APA

IUCN. (1973). A System for defining and classifying natural regions for purposes of conservation. [S.l.]: [s.n.].

Citación estilo Chicago

IUCN. A System for Defining and Classifying Natural Regions for Purposes of Conservation. [S.l.]: [s.n.], 1973.

Cita MLA

IUCN. A System for Defining and Classifying Natural Regions for Purposes of Conservation. [S.l.]: [s.n.], 1973.