1. T. Janssen and H. Schneider, Plant Syst. Evol., 252, 175 (2005).
2. D. T. Loi, Medicinal Plants and Remedy of Vietnam, Publisher of Medicine, Hanoi, 2004, p. 491.
3. P. H. Ho, Vietnamese Plants, 1, Publisher of Young, Hanoi, 2002, p. 83.
4. P. T. N. Trinh, N. C. Hao, and P. T. Thao, Vietnam J. Chem., 47 (4A), 463 (2009).
5. P. T. N. Trinh, N. C. Hao, and P. T. Thao, Vietnam J. Chem., 47 (4A), 468 (2009).