1. Yoda, K., Kira, T., Ogawa, H. & Hozumi, K. J. Biol. Osaka Cy Univ. 14, 107–129 (1963).
2. Ondok, J. P. in Ecosystem Study on Wetland Biome in Czechoslovakia (ed. Hejný, S.) 83–85 (Czechosl. IBP/PT-PP Rep. no. 3, Třeboň 1973).
3. Mörnsjö, T. Opera bot. No. 24, pp 187 (1969).
4. Gorham, E. & Bernard, J. M. J. Minn. Acad. Sci. 41, 15–17 (1975).
5. Bernard, J. M. & MacDonald, J. G. Jr, Can. J. Bot. 52, 117–123 (1974).