Seven New Secoiridoids with Anti-Hepatitis B Virus Activity from Swertia angustifolia - He, Kang; Ma, Yun-Bao; Cao, Tuan-Wu; Wang, Hong-Ling; Jiang, Fu-Qiang; Geng, Chang-An; Zhang, Xue-Mei; Chen, Ji-Jun (Planta Medica, 2012)