I thank Don Johnson for the Sardi piece. One of the footnotes intrigues me:

14. “Terra Incognita” was said to be inspired by Joseph Conrad’s similar novella, “An Outpost of Progress” (1896), in which the author relates his own experiences in the Congo. Concordances with Conrad’s Heart of Darkness are also relevant at this point.

Does anyone know where this claim originates?

Many thanks,
Piers Smith