1. N. G. Kovaleva, in: Medicinal Plants [in Russian], Moscow (1971), p. 34.
2. A. F. Gamerman and P. I. Grom, Wild Medicinal Plants of the USSR [in Russian], Moscow (1976), p. 132.
3. J. Macku and J. Kreča, in: Atlas of Medicinal Plants [in Czech], Bratislava (1970), p. 186.
4. V. Florya, in: Medicinal Plants [in Russian], Kishinev (1976), p. 224.
5. E. V. Kucherov, G. K. Baikov, and I. B. Gufranov, in: Useful Plants of the Southern Urals [in Russian], Moscow (1976), p. 135.