Hallbdcken L, Zhang LQ. Effects of experimental acidification, nitrogen addition and liming on ground vegetation in a mature stand of Norway spruce (Picea abies (L.) Karst.) in SE Sweden. Forest Ecology and Management . 1998  ;108:201-213.

Hallbdcken L, Kellner O. Effects of simulated nitrogen rich and acid rain on the nitrogen-fixing lichen Peltigera aphthosa (L.) Willd. . New Phytologist. 1992  ;120:99-103.