[17] Frobenius: _Voice of Africa_, II, 359-360. [18] Ibn Khaldun, quoted in Lugard, p. 128. [19] Quoted in Lugard, p. 180. [20] Es-Sa 'di, quoted by Lugard, p. 199. [21] Lugard, p. 373. [22] Mungo Park, quoted in Lugard, p. 374.