TY - Generic T1 - Lichens as bioindicators of sulfur dioxide Y1 - 2002 A1 - Nash, T.H. A1 - Gries, C. JF - Symbiosis VL - 33(1) ER - TY - Generic T1 - Effect of ozone on gross photosynthesis of lichens Y1 - 1983 A1 - Ross, L.J. A1 - Nash, T.H. JF - Environmental and Experimental Botany VL - 23 ER -