T. D. V.  Swinscow and Krog, H., Macrolichens of East Africa. Dorchester: Henry Ling Ltd, The Dorset Press, 1988.

O.  Gilbert, Lichens. London: HarperCollins, 2000, p. 288.

T. H.  Nash_, III, Ryan, B. D., Gries, C., and Bungartz, F., Lichen Flora of the Greater Sonoran Desert Region, vol. 1. Tempe: Lichens Unlimited, 2001.

I. M.  Brodo, Sharnoff, S. Duran, Laurie-Bourque, S., and Sharnoff, S., Lichens of North America. Yale University Press, 2001.

?Index Fungorum [taxonomy information]?, 2008.