"The Southern Slope of Mount Cameroon" (1885)
Der Süd-Abhang des Kamerun-Gebirges nach Dr H. Zöller's Originalkarten und Berichten sowie allen vorhandenen Quellen entworfen und gezeichnet von P. Langhans; Masstab 1:200.000, Source: Petermann's Geographische Mitteilungen, Tafel 18, Gotha, Justus Perthes 1885.
Marmocchi, Francesco C., "La Guinea"
Source: Il Globe Atlante di Carte Geografiche Compilate da P.C. Marmocchi per servire di corredo al suo Corso di Geografia Commerciale (Genova, Paolo Rivara fu Giacomo Editore 1885, Torino, Lit. Giordana e Sabussolia), Scale 1:11,400,000.
"West Coast of Africa from the Cape Verd Islands to the Congo River, Illustrating the Botany of the Niger Expedition"
Source: William Jackson Hooker (ed.), Niger flora; or, An enumeration of the plants of western tropical Africa (London: Hippolyte Bailliere, 1849), p. 72.