1. Derome, J., Kukkola; M. and Mälkönen, E.: 1986, Forest liming on mineral soils, Nat. Swed. Env. Prot. Board, 3084
2. Helmisaari, H-S. and Mälkönen, E.: 1989, Scandinavian J. of Forest Res., 4, 1
3. Nilsson, S.I. and Bergkvist, B.: 1983, Water Air and Soil Pollution, 20, 311
4. Nilsson, S.I., Wiklander, G. and Farrel, E.P.: 1983 For. Ecol. Manage., 5, 87
5. Schnitzer, M. and Khan, S.U. 1972: Humic Substances in the Environment, Marcel Dekker Inc., New York