H.  Kristinsson, ?The lichen flora of the outer Hvalfjördur area in West Iceland?, Acta Botanica Islandica, vol. 8, pp. 31-50, 1985.

O. W.  Purvis, Moore, D. M., Coppins, B. J., Hawksworth, D. L., and James, P. W., The Lichen Flora of Great Britian and Ireland. London: Natural History Museum Publications, 1992.

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.

J. W.  Thomson and Ahti, T., ?Lichens Collected on an Alaska Highway Expedition in Alaska and Canada?, The Bryologist, vol. 97, pp. 138-157, 1994.

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.

?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.