Combination of capillary GC, GC/MS and 13C-NMR for the characterization of the rhizome oil of Piper betle L. (Piperaceae) from Vietnam - Thanh, Lê; Dung, Nguyên Xuân; Bighelliand, Ange; Casanova, Joseph; Leclercq, Piet A. (Spectroscopy, 1997)