Use of high-performance liquid chromatography-tandem mass spectrometry to distinguish Panax ginseng C. A. Meyer (Asian ginseng) and Panax quinquefolius L. (North American ginseng) - Li, W; Gu, C; Zhang, H; Awang, D V; Fitzloff, J F; Fong, H H; van Breemen, R B (Anal Chem, 2000)