1. Martindale's Extra Pharmacopeia (28th ed.), Pharmaceutical Press, London (1982).
2. L. A. Baltina, N. G. Serdyuk, N. A. Somov, Yu. I. Murinov, and G. A. Tolstikov, in: The Study and Use of Licorice in the National Economy of the USSR [in Russian], Gylym, Alma-Ata (1991), p. 140.
3. L. V. Krasnova, A. A. Berg, L. I. Afanas'ev, L. A. Baltina, and Yu. I. Murinov, ibid., p. 126.
4. G. A. Tolstikov, U. M. Dzhemilev, D. Ya. Soshnikov, A. G. Petunina and A. Sh. Yukhanova, Method of Isolating Glycyrrhizic Acid [in Russian], USSR Inventors' Certificate 419521 (applied for: June 14, 1972).
5. I. Tosisuke, Japanese Patent 15875 (October 21, 1960); Ref. Zh. Khim., 10N222P (1963).