1. P. S. Hsu, J. Q. Hu, and H. J. Wang, Flora Reipublicae Popularis Sinicae, Science Press, Beijing, Vol. 72, 1988, 105 pp.
2. Z. J. Guo, J. X. Wang, Y. F. Su, Y. X. Wei, and Y. H. Zhu, Shaanxi Qiyao, Shaanxi Science and Technology Press, Shaanxi, 2003, 49 pp.
3. X. Chai, Y. F. Su, Y. H. Zheng, S. L. Yan, X. Zhang, and X. M. Gao, Biochem. Syst. Ecol., 38, 210 (2010).
4. H. Tomita and Y. Mouri, Phytochemistry, 42, 239 (1996).
5. M.-C. Recio-Iglesias, A. Marston, and K. Hostettmann, Phytochemistry, 31, 1387 (1992).