APA

Gifford E. W., . (1913). The birds of the Galapagos Islands, with observations on the birds of Cocos and Clipperton Islands (Columbiformes to Pelicaniformes). [S.d: s.d.].

Chicago

Gifford E W, . 1913. The birds of the Galapagos Islands, with observations on the birds of Cocos and Clipperton Islands (Columbiformes to Pelicaniformes). [S.d: s.d.].

Harvard

Gifford E. W., . (1913). The birds of the Galapagos Islands, with observations on the birds of Cocos and Clipperton Islands (Columbiformes to Pelicaniformes). [S.d: s.d.].

MLA

Gifford E W, . The birds of the Galapagos Islands, with observations on the birds of Cocos and Clipperton Islands (Columbiformes to Pelicaniformes). [S.d: s.d.]. 1913.