Erskine, « Journey of Exploration to the Mouth of the River Limpopo », The Journal of the Royal Geographical Society of London, vol. 39, , p. 233–276 (DOI10.2307/1798552, JSTOR1798552)
Erskine, « Journey of Exploration to the Mouth of the River Limpopo », The Journal of the Royal Geographical Society of London, vol. 39, , p. 233–276 (DOI10.2307/1798552, JSTOR1798552)