* Overbergh (editor), "Collection de monographies ethnographiques" (Brussels, 1907–11)* Ó Síocháin, Séamas and Michael O’Sullivan, eds: "The Eyes of Another Race: Roger Casement's Congo Report and 1903 Diary".
* Overbergh (editor), "Collection de monographies ethnographiques" (Brussels, 1907–11)* Ó Síocháin, Séamas and Michael O’Sullivan, eds: "The Eyes of Another Race: Roger Casement's Congo Report and 1903 Diary".