J. Walter Thomson and Brehmer, B., American Arctic Lichens I. The Macrolichens. Columbia University Press, 1984.

J. W.  Thomson and Weber, W. A., ?Lichens Collected on the Arctic Excursion of the 9th International Botanical Congress (Montreal) in 1959?, The Bryologist, vol. 95, pp. 392-405, 1992.

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.

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.

T.  H. Lumbsch and Huhndorf, S. M., ?Outline of Ascomycota - 2007. [Classification Information]?, Myconet, vol. 13, pp. 1-58, 2007.

J. W.  Hinds and Hinds, P. L., The Macrolichens of New England, vol. 96. China: The New York Botanical Garden Press, 2007.