APA

Christophersen E., . (1932). A collection of plants from the Galápagos Islands. : .

Chicago

Christophersen E, . 1932. A collection of plants from the Galápagos Islands. : .

Harvard

Christophersen E., . (1932). A collection of plants from the Galápagos Islands. : .

MLA

Christophersen E, . A collection of plants from the Galápagos Islands. : . 1932.