Larsen J, Birksl HJB, Raddum G, Fjellheim A. Quantitative relationships of invertebrates to pH in Norwegian river systems. Hydrobiologica. 1996  ;328:57-74.

Raddum G, Skjelkvale BL. Critical limits of acidification to invertebrates in different regions of Europe. Water Air and Soil Pollution. 1995  ;85:475-480.