Reference
Natalia Tkach, Bettina Heuchert, Christina Krüger, Heike Heklau, Denise Marx, Uwe Braun, Martin Röser (2016): Type material in the herbarium of the Martin Luther University Halle-Wittenberg of species based on collections from Alexander von Humboldts American expedition between 1799 and 1804 in its historical context – Schlechtendalia – 29: 1 - 107.