1. Arb C von, Brunold C (1989) Lichen physiology and air pollution. I. Physiological responses of in situ Parmelia sulcata among air pollution zones within Biel, Switzerland. Can J Bot 68: 35?42
2. Beevers L, Hageman RH (1980) Nitrate and nitrite reduction. In: Miflin BJ (ed) The biochemistry of plants, vol 5. Academic, New York
3. Bradford MM (1976) A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye-binding. Anal Biochem 72: 248?254
4. Schriftenreihe Umwelt;BUWAL,1991
5. Durmishidze SV, Nutsubidze NN (1976) Absorption and conversion of nitrogen dioxide by higher plants. Dokl Biochem 277: 104?107