1. Der natürliche Kreislauf der Gase
2. The Carbon Dioxide Question
3. Spektrum der Wissenschaft, Erstedition 1978, p. 1, and references cited therein.
4. in : Air Pollution Control. Part II. Wiley, New York 1972.
5. : Air Pollution. Vol. I. 3rd Edit. Academic press, New York 1976.