1. Air Pollution Across National Boundaries, Sweden's case study for the U.N. Conference on the human environment, Stockholm (1971).
2. Anschütz, I. and Gessner, F.: 1954,Flora 141, 178.
3. Clymo, R. S.: 1963,Ann. Bot. 27, 309.
4. Gelting, G. and Pontén, A.: 1971,Inst. Plant Ecol., Uppsala (mimeogr. rep.).
5. Goodman, G. T. and Roberts, T. M.: 1971,Nature 231, 287.