- IPNI Life Sciences Identifier (LSID)
- Sweet's Hortus Britannicus: or, a catalogue of all the plants indigenous or cultivated in the gardens of Great Britain, arranged according to the natural system / by Robert Sweet. 3d. ed., greatly enl. and improved. Ed. by George Don, F. L. S. London
D. Don (in Sweet, Brit. Fl. Gard. 4(ser. 2, 1): sub t. 87. Mar 1831) doubtfully assigned Rudbeckia radula to Centrocarpha, but did not make the comb. nov.