Hardenburg, W. E. (1912). The Putumayo: The devil's paradise. Travels in the peruvian Amazon region and an account of the atrocities committed upon the indians therein, together with extracts from the report of Sir Rogers Casement confirming the occurrences. T. Fisher Unwin.
Tohutoru Kātū Chicago (17th ed.)Hardenburg, W. E. The Putumayo: The Devil's Paradise. Travels in the Peruvian Amazon Region and an Account of the Atrocities Committed upon the Indians Therein, Together with Extracts from the Report of Sir Rogers Casement Confirming the Occurrences. London, England, United Kingdom: T. Fisher Unwin, 1912.
Tohutoro MLA (9th ed.)Hardenburg, W. E. The Putumayo: The Devil's Paradise. Travels in the Peruvian Amazon Region and an Account of the Atrocities Committed upon the Indians Therein, Together with Extracts from the Report of Sir Rogers Casement Confirming the Occurrences. T. Fisher Unwin, 1912.