Impact of four years exposure to different levels of ozone, phosphorus and drought on chlorophyll, mineral nutrients, and stem volume of Norway spruce, Picea abies. - Wallin,G..; Karlsson,P..E..; Sellden,G..; Ottosson,S..; Medin,E..L..; Pleijel,H..; Skärby,L.. (Physiologia Plantarum, 2002)