Literature 

On observation

• Bockemühl, J., 1980. In partnership with nature. BioDyn Farming Ass., Spring Valley, N.Y.
• Bockemühl, J., 1990. Dying forests. Anthroposophic Press, Spring Valley, N.Y.
• Bockemühl, J. et al, 1985. Elements and ethers: modes of observing the world. In: Bockemühl, J. (ed). Toward a phenomenology of the etheric world. Anthroposophic Press, Spring Valley, N.Y.
• Colquhoun, M. & A. Ewald, 1996. New Eyes for Plants – A workbook for observing and drawing plants. Hawthorn Press, Strout.
• Romunde, Dick van, 2000. Over vormende krachten in de Plantenwereld. Louis Bolk Instituut, Driebergen.
• Seamon, D. & A. Zajonc, 1998. Goethe's way of science. State Univ. of N.Y. Press, Albany.
• Steiner, R. 1920. The boundaries of natural science. Especially the 8th lecture. Rudolf Steiner Press, London.

On the senses

• Aeppli, W., 1993. Care and development of the human senses. Steiner School Fellowship Publications.
• Kranich, E.M., 2003. Der innere Mensch und sein Leib – Eine Anthropologie. Freies Geistesleben, Stuttgart.
• Schoorel, E., 20002. De eerste zeven jaar – Kinderfysiologie. Christofoor, Zeist.
• Soesman, A., 1999. Our twelve senses. Hawthorn Press, Stroud.
• Steiner, R., Man as being of sense and perception. Rudolf Steiner Press, London.