1. Advances in Chemistry Series,1975
2. Barkman, J. J.: 1958, Phytosociology and Ecology of Cryptogamic Epiphytes, Van Gorcum & Company, The Netherlands.
3. Crock, J. G., Lichte, F. E., and Briggs, P. H.: 1983, Geostandards Newsletter
7, 335.
4. Erdman, J. A. and Gough, L. P.: 1977, The Bryol.
80, 492.
5. Ferry, B. W., Baddeley, M. S., and Hawksworth, D. L. (eds.): 1973, Air Pollution and Lichens, University of Toronto Press, Toronto.