1. Hahnemann S: Organon of Medicine. Bucks, Beaconsfield, 1984.
2. Kent JT: Lectures on Homoeopathic Materia Medica with New Remedies. New Dehli, B. Jain, 1904.
3. Boericke W: Homoeopathic Materia Medica. Philadelphia, Boericke and Runyon, 1927.
4. Vermeulen F: Concordant Materia Medica. Haarlem, Merlijn, 1994.
5. Dantas F, Fisher P: A systematic review of homeopathic pathogenic trials (`provings') published in the United Kingdom from 1945 to 1995; in Ernst E (ed): Homoeopathy: a Critical Appraisal. London, Butterworth Heinemann, 1998, pp 69-97.