Application of Electrospray Ionization Mass Spectrometry Combined with Sequential Tandem Mass Spectrometry Techniques for the Profiling of Steroidal Saponin Mixture Extracted from Tribulus terrestris - Fang, Shiping; Hao, Chunyan; Liu, Zhiqiang; Song, Fengrui; Liu, Shuying (Planta Medica, 1999)