Weinstein LH, Laurence JA.
Indigenous and cultivated plants as bioindicators. In: Biologic Markers of Air-Pollution Stress and Damage in Forests. Biologic Markers of Air-Pollution Stress and Damage in Forests. Washington DC: National Academy Press; 1989. pp. 194-204.
Westling O.
Nitrate in soil water. Göteborg: IVL Swedish Environmental Research Institute; 1991 pp. pp 1-20.
WHO.
Air Quality Guidelines for Europe. . Copenhagen: World Health Organisation; 2000.
WHO.
Environmental Health Criteria 221 Zinc. Geneva: World Health Organisation; 2001.
WHO.
Effects of atmospheric nitrogen compounds (particularly nitrogen oxides) on plants. In: Environmental Health Criteria Series. Vol. 188. Environmental Health Criteria Series. Geneva: WHO; 1997. pp. 115–191.
WHO.
Environmental Health Criteria 200 Copper. Geneva: World Health Organization; 1998.