Multistage and tandem mass spectrometry of glycosylated triterpenoid saponins isolated from Bacopa monnieri: comparison of the information content provided by different techniques - Zehl, M; Pittenauer, E; Jirovetz, L; Bandhari, P; Singh, B; Kaul, V K; Rizzi, A R; Allmaier, G (Anal Chem, 2007)