Figlar & Noot. (Dandy) 2004 - Figlar RB, Nooteboom HP (2004) Notes on Magnoliaceae IV. Blumea - Biodiversity, Evolution And Biogeography of Plants 49(1): 87-100. doi: 10.3767/000651904x486214.
There is no corrections for Magnolia sumatrae yet.