References
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- Nygaard, G. 1955. On the productivity of five Danish waters. — Verh. internat. Ver. Limnol. 12, 123–133.
- Steemann Nielsen, E. 1944. Dependence of freshwater plants on quantity of carbon dioxide and hydrogen ion concentration. Illustrated through experimental investigations. — Dansk Botanisk Arkiv 11 (8), 1–25.
- Steemann Nielsen, E. 1947. Photosynthesis of aquatic plants with special reference to the carbon-sources. – Dansk Botanisk Arkiv 12 (8), 1–71.