*G. Schweinfurth: _The Heart of Africa_, Vol. II, 1873.
*H.M. Stanley: _Through the Dark Continent_, 2 vols., 1878.
---- _In Darkest Africa_, 2 vols., 1890.
---- _The Congo_, etc., 2 vols., London, 1885.
H. von Wissman: _My Second Journey through Equatorial Africa_, 1891.
*H.R. Fox-Bourne: _Civilization in Congoland_, 1903.
Sir Harry H. Johnston: _George Grenfell and the Congo_, 2 vols., London,
1908.
*E.D. Morel: _Red Rubber_, London, 1906.