the latter method, a solution of copper chloride and the test solution is allowed to evaporate. The pattern of the copper chloride crystals can be "read" based on the patterns of known samples. Similarly, the patterns of the circular chromatographs can be "read" based on known samples. Both methods require much practice to "read" and interpret the images. Honorary degree Pfeiffer's work at Hahnemann earned him an honorary Doctor of Medicine (M.D.) degree from Hahnemann Medical College and Hospital of Philadelphia on June 8, 1939, at its 91st commencement ceremony. Books and articles by Ehrenfried Pfeiffer Biodynamics in farming and gardening Ehrenfried Pfeiffer, Soil Fertility, Renewal and Preservation: Bio-Dynamic Farming and Gardening, Asiatic Publishing House, 2006. . ————, Bio-Dynamic Gardening and Farming: Articles, Mercury Press, 1983-1984. . ————, Using the Bio-Dynamic Compost Preparations & Sprays in Garden, Orchard & Farm, Biodynamic Farming & Gardening Association, 1984. . Ehrenfried Pfeiffer and Erika Riese, Grow a Garden and Be Self-Sufficient, Mercury Press, 1981. . ————, Bio-Dynamics: Three Introductory Articles, Charter, 1999. ASIN B000PIZ250. ————, The Biodynamic Treatment of Fruit Trees, Berries and Shrubs, Biodynamic Farming & Gardening Association, 1976. ————, Weeds and What They Tell, Biodynamic Farming & Gardening Association, 1981. ASIN B00071HRSU. ————, The Earth's Face: Landscape and Its Relation to the Health of the Soil, Faber and Faber, 1947. ASIN B0007IXST0. ————, Practical Guide to the Use of the Bio-Dynamic Preparations, Rudolf Steiner Publishing, 1945. ASIN B0007K8FAU. ————, The Fair Garden Plot: Concise Guidance for Growing One's Own Vegetables, Rudolf Steiner Publishing, 1945. ASIN B0007KD2GC. Chromatography ————, Chromatography Applied to Quality Testing, Biodynamic Farming & Gardening Association, 1984. ————, Sensitive Crystallization Processes: A Demonstration of Formative Forces in the Blood, Anthroposophic Press, 1975. ASIN B00073467S. Composting ————, The Art and Science of Composting: Observations and Testing Methods: The Chromatographic Method, Biodynamic Farming & Gardening Association, 1959. ASIN B0007HK7MC. ————, The Compost Manufacturers Manual: The Practice of Large Scale Composting, Pfeiffer Foundation, 1956. ASIN B0007G1MWC. Other topics ————, Heart Lectures: Three Lectures, Mercury Press, 1982. . ————, The Chymical Wedding of Christian Rosenkreutz: A Commentary, Mercury Press, 1984. . ————, Zarathustrian Way, St. George Book Service, 1982. . ————, On Rudolf Steiner's Mystery Dramas, Four Lectures Given in Spring Valley, 1948. Mercury Press, See also Biodynamic Farming & Gardening Association Biodynamic Agriculture Demeter International References Biographical resources Ehrenfried Pfeiffer, Ein Leben fur den Geist: Ehrenfried Pfeiffer (1899-1961): Pfeiffers autobiographische Erinnerungen, Aufzeichnungen