J.G. Baker: Refugium Botanicum; or, Figures and Descriptions from Living Specimens of Little Known of New Plants of Botanical Interest.Volume 3, Tafel 199, 1870 London online (PDF; 9,6 MB)
biodiversitylibrary.org
Édouard Morren: La Belgique Horticole. Volume 24, S. 158, 1874 online