L. E.  Urbatsch, Roberts, R. P., and Karaman, V., ?Phylogenetic evaluation of Xylothamia, Gundlachia, and related genera (Asteraceae, Astereae) based on ETS and ITS nrDNA sequence data?, Am. J. Bot, vol. 90, no. 4, pp. 634 - 649, 2003.