APA Citation

Helbig, K. (1935). Die insel Sumatra. [s.l.]: [s.n.].

Chicago Style Citation

Helbig, K. Die Insel Sumatra. [s.l.]: [s.n.], 1935.

MLA Citation

Helbig, K. Die Insel Sumatra. [s.l.]: [s.n.], 1935.

Warning: These citations may not always be 100% accurate.