D. J.  Galloway and James, P. W., ?The Lichen Genus Psoromidium Stirton?, The Lichenologist, vol. 17, pp. 173-188, 1985.

D. J.  Galloway, Henssen, A., Renner, B., Marton, K., and James, P. W., ?Studies in the lichen genus Psoroma 2. Psoroma fruticulosum and Psoroma rubromarginatum?, Mycotaxon, vol. 18, pp. 29-48, 1983.

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.

P. M.  Jørgensen and James, P. W., ?Studies in the lichen family Pannariaceae IV: The genus Degelia?, Bibliotheca Lichenologica, vol. 38, pp. 253-276, 1990.