Grey , H. M. (1927). The land of to-morrow: A mule-back trek through the swamps and forests of Eastern Bolivia. H.F. and G. Witherby.

Grey , Henry M. The Land of To-morrow: A Mule-back Trek Through the Swamps and Forests of Eastern Bolivia. London: H.F. and G. Witherby, 1927.

Grey , Henry M. The Land of To-morrow: A Mule-back Trek Through the Swamps and Forests of Eastern Bolivia. H.F. and G. Witherby, 1927.