https://honighaeuschen.de/produkt/orchidaceae-of-west-central-africa-southern-chad-cameroon-central-african-republic-sao-tome-and-principe-equatorial-guinea-gabon-republic-of-the-congo-democratic-republic-of-the-congo-nort/
Orchidaceae of West – Central Africa. (Southern Chad, Cameroon, Central African Republic, Sao Tomé and Principe, Equatorial Guinea, Gabon, Republic of the Congo, Democratic Republic of the Congo, Northern Angola). Volume 3. Vandoideae (continued).