1. Y. X. Cheng, J. Zhou, N. H. Tan, and Z. T. Ding, Chin. Chem. Lett., 11, 59 (2000).
2. Y. Cheng, J. Zhou, and N. Tan, Acta Bot. Sin., 43, 760 (2001).
3. Y. X. Cheng, J. Zhou, N. H. Tan, Y. Lu, X. Liu, and Q. Zheng, Heterocycles, 55, 194 (2001).
4. J. Zhao, L. Zhou, X. Li, H. Xiao, F. Hou, and Y. Cheng, J. Nat. Prod., 74, 1392 (2011).
5. H. Hu, J. Xue, B. M. Swarts, Q. Wang, Q. Wu, and Z. Guo, J. Med. Chem., 52, 2052 (2009).