H.  Riedl, ?Boraginaceae?, in Flora Malesiana, Series I ? Seed Plants, vol. 13, C.  Kalkman, Kirkup, D. W., Nooteboom, H. P., Stevens, P. F., and de Wilde, W. J. J. O., Eds. Leiden: Rijksherbarium / Hortus Botanicus, 1997, pp. 43 - 144.